Model Paper 5

Chapter 6 · Full Model Papers · 200 questions in the paper · 40 min read

Model Paper 5

What the syllabus asks for 1
  • Zoology 40, Botany 40, Chemistry 50, Physics 50, Mental Agility Test 20, with an explained key

MODEL PAPER 2 — MECEE-BL (Group I). Time: 3 hours. Full marks: 200. Attempt all questions. Each question has four options with one best answer; choose the best and mark it on your answer grid. Each correct answer carries 1 mark and each wrong answer deducts 0.25 mark. Calculators are not allowed; do rough work in the margins. Sit this paper in one uninterrupted sitting, exactly as on the day.

How to score yourself: score = (number correct) − 0.25 × (number wrong). Do not leave blanks — in this marking scheme even a blind guess is worth +1/16 of a mark. Record your correct/wrong/blank counts per subject before you open the key.

This paper follows the official unit weightage exactly:

Subject Qs Per-unit counts in this paper
Zoology 40 Evolution 3 · Diversity 4 · Tissues 4 · Selected animals 6 · Digestive 2 · Respiratory 2 · Circulatory 3 · Excretory 2 · Nervous 2 · Endocrine 2 · Reproductive 2 · Diseases/Immunity 4 · Medical technology 2 · Environment 2
Botany 40 Components of life 2 · Virus/bacteria 2 · Fungi/lichens 2 · Algae/bryophytes 2 · Pteridophytes–angiosperms 3 · Ecology 4 · Cell biology 5 · Genetics fundamentals 2 · Genetic material 4 · Anatomy 3 · Water relations 2 · Photosynthesis/respiration 3 · Growth 1 · Developmental 2 · Applied 3
Chemistry 50 Physical 17 · Inorganic 10 · Organic 17 · Applied 3 · Analytical 3
Physics 50 Mechanics 10 · Heat 7 · Waves/Optics 8 · Current electricity/Magnetism 9 · Electrostatics 4 · Modern 12
MAT 20 Verbal 5 · Numerical 5 · Logical 5 · Spatial/Abstract 5

Zoology (questions 1–40)

  1. The scientific study of fossils is calledaembryologybpalaeontologyctaxonomydphysiology
  2. Among living animals, the closest evolutionary relative of human beings is theamonkeybchimpanzeecgibbondlemur
  3. In modern evolutionary theory, the unit in which gene frequencies change (the unit of evolution) is theaindividualborganccelldpopulation
  4. Insects breathe through a network of air tubes opening outside by spiracles, thealung systembgill systemctracheal systemdskin system
  5. Coral reefs are built up by the skeletons of colonialaspongesbmolluscsccnidarian polypsdechinoderms
  6. The only mammal capable of true (powered) flight is theaflying squirrelbostrichcpenguindbat
  7. Amphioxus (the lancelet) is placed in the chordate subphylumaUrochordatabVertebratacCephalochordatadHemichordata
  8. A basement membrane characteristically supports and underliesamuscle fibres onlybcartilagecblooddepithelial tissue
  9. The involuntary, non-striated muscle of the gut wall and the iris isaskeletal musclebcardiac musclecstriated voluntary muscledsmooth muscle
  10. Gap junctions between neighbouring animal cells mainly allowarapid passage of ions and small molecules between thembmovement of whole chromosomes from cell to cellcexchange of ribosomes through membrane fusionsdtransport of proteins along cytoskeletal tracks
  11. New bone matrix is laid down by the cells calledamature osteocytesbosteoclastscosteoblastsdchondroblasts
  12. The most dangerous (malignant) malaria of human beings is caused by Plasmodiumavivaxbfalciparumcovaledmalariae
  13. The fever paroxysms of malaria coincide with theaentry of sporozoites into liver cellsbformation of gametocytes in the bloodcbite of an infected female Anophelesdrupture of infected red blood cells releasing merozoites and toxins
  14. The chloragogen cells around the intestine of the earthworm perform a function similar to that of the vertebratealiver (storage of glycogen and fat)bkidney (filtration of the blood)clung (exchange of respiratory gases)dheart (pumping of blood in the body)
  15. An earthworm left on hot, dry soil soon dies even though air is plentiful, mainly becauseaits heart stops in the absence of waterbgas exchange through its skin needs a moist surfacecits setae cannot grip dry soil for movementddry air destroys its haemoglobin at once
  16. The tongue of the frog is attached to the floor of the mouth at theaat the back, and is free in the frontbin the middle, free at both of the endscalong the sides, and free in the middledat the front, and is free and forked behind
  17. During hibernation (winter sleep), the frog respires mainly through itsalungsbbuccal cavitycexternal gillsdskin
  18. Absorption of vitamin B₁₂ from the gut requires the intrinsic factor secreted by theastomachblivercpancreasdlarge intestine
  19. Peristalsis moves food along the alimentary canal by means ofathe beating of cilia lining the whole gutbrhythmic muscular contractions of the gut wallcthe pull of gravity acting on the food massdsuction pressure developed by the stomach
  20. The oxygen–haemoglobin dissociation curve of human blood has the shape described asaa straight line rising steadily with pressureba rectangular hyperbola levelling rather earlyca steadily declining curve over the whole rangedsigmoid (S-shaped), owing to cooperative binding
  21. In the lung disease emphysema, the structures chiefly damaged (reducing surface for exchange) are theabronchi onlybpleural membranescwalls of the alveolidcartilages of the trachea
  22. The P wave of a normal ECG represents the electrical activity ofaventricular contractionbatrial depolarisationcventricular repolarisationdthe AV nodal delay
  23. The normal arterial blood pressure of a healthy young adult is abouta120/80 mm Hgb80/120 mm Hgc160/40 mm Hgd100/100 mm Hg
  24. Exchange of materials between blood and tissues occurs across the capillaries because their walls areathick and muscularbonly one cell thickcprovided with valvesdmade of cartilage
  25. Glucose does not appear in normal urine because it is completely reabsorbed in theaurinary bladderbloop of Henle onlyccollecting ductdproximal convoluted tubule
  26. The osmotic gradient of the kidney medulla, needed to concentrate urine, is set up mainly by the countercurrent flow in thearenal pelvisburetercglomerulidloops of Henle
  27. In the central nervous system, the myelin sheath of axons is formed by the glial cells calledaoligodendrocytesbSchwann cellscneuron cell bodiesdastrocyte end-feet
  28. The semicircular canals of the internal ear are concerned withahearing sounds of very high frequencybbalance of the body during movement/rotationcthe chemical sense of smell and tastedfocusing of the eye on distant objects
  29. Follicle-stimulating hormone (FSH) is secreted by theaposterior pituitarybovarycanterior pituitarydadrenal cortex
  30. Parathormone (PTH) regulates metabolism by acting toadecrease blood calciumblower the blood glucosecraise the blood calcium leveldincrease urine output always
  31. In a normal 28-day human menstrual cycle, ovulation occurs at about thea14th dayb1st dayc28th dayd5th day
  32. The placenta is also an endocrine organ; during early pregnancy it secretes the hormoneainsulin from the islets of Langerhansbtestosterone from the interstitial cellschuman chorionic gonadotropin (hCG)dadrenaline from the adrenal medulla
  33. Tetanus (lockjaw) is caused by the toxin of the bacteriumaVibrio choleraebClostridium tetanicMycobacteriumdSalmonella
  34. Passive immunity is obtained when a person is givenaready-made antibodies (for example an antiserum)ba vaccine made of killed disease microbesca mild natural infection with the pathogenda course of antibiotics against bacteria
  35. The poliomyelitis virus causes paralysis by destroyingacells of the liverbred blood cellscmotor neurons of the spinal corddcells of the alveoli
  36. Leprosy (Hansen's disease) is caused byaa virusbMycobacterium lepraeca fungusda protozoan
  37. Amniocentesis, sampling the amniotic fluid, is used mainly to detect in the foetusachromosomal and genetic abnormalitiesbthe blood pressure of the mothercthe blood group onlydcauses of infertility
  38. An artificial cardiac pacemaker, implanted in a patient, works byagenerating timed electrical impulses to regulate the heartbeatbpumping the blood mechanically in place of the heartcfiltering waste products out of the blood continuouslydserving only to measure and record the blood pressure
  39. "Sustainable development", in the Brundtland sense, means development thatamaximises growth in the present onlybstops all use of resourcescmeets present needs without compromising future generationsdpreserves wildlife but ignores people
  40. In Nepal, the greater one-horned rhinoceros is protected principally in theaChitwan National ParkbSagarmatha National ParkcShey-Phoksundo National ParkdKhaptad National Park

Botany (questions 41–80)

  1. Starch is a polymer built from units ofaglucosebfructosecgalactosedamino acids
  2. Vitamin C is chemically known asafolic acidbcitric acidcacetic aciddascorbic acid
  3. Which of the following plant diseases is caused by a virus?aLate blight of potatobTobacco mosaiccRust of wheatdSmut of maize
  4. The bacterium that sours milk to form curd (yoghurt) isaRhizobiumbNitrosomonascLactobacillusdClostridium
  5. Fungi store their reserve food mainly in the form ofaglycogenbstarchccellulosedsucrose
  6. The rust disease of wheat is caused by the fungusaAlbugobPucciniacUstilagodErysiphe
  7. The red colour of red algae (Rhodophyta) is due to the pigmentachlorophyll alonebfucoxanthincxanthophylldphycoerythrin
  8. In the sporophyte of a moss, the stalk that bears the capsule is theafootbsetacapophysisdcolumella
  9. Sori, found on the underside of fern fronds, are clusters ofasporangiabseedscconesdarchegonia
  10. Parallel venation of the leaf is a usual character ofadicotyledonsbfernscmonocotyledonsdgymnosperms
  11. The grain fruit of grasses (family Poaceae), in which the seed coat is fused with the fruit wall, is called aalegumebcapsuleccaryopsisddrupe
  12. A population in ecology is a group of organisms ofathe same species living in an areaball species of an areacplants and soil togetherda single individual organism
  13. An interaction between two species in which both partners benefit is termedamutualismbparasitismccommensalismdpredation
  14. The ozone layer of the stratosphere is valuable to life because itait keeps the ground warm like a blanketbit is the main cause of photochemical smogcit dissolves in rain producing acid raindabsorbs harmful ultraviolet radiation
  15. Plants that grow naturally in salty marshes and saline soils are calledahydrophytesbhalophytescxerophytesdlithophytes
  16. Proteins of the cell are synthesised on the surfaces of theamitochondriablysosomescribosomesdGolgi vesicles only
  17. The middle lamella that cements two plant cell walls together is composed chiefly ofaligninbcalcium pectatecsuberindchitin
  18. Pairing (synapsis) of homologous chromosomes in meiosis takes place during thealeptotene stagebpachytene stageczygotene stageddiplotene stage
  19. During mitosis, the spindle fibres attach to each chromosome at itsacentromere (kinetochore)btelomerecchromatid tipdnucleolus
  20. Root hairs continue absorbing nitrate ions from a very dilute soil solution even when the cell sap already contains much more nitrate, but this uptake stops if respiration is poisoned with cyanide. The uptake is therefore an example ofasimple diffusion down a gradientbosmosis through the cell wallcmass flow with transpirationdactive transport using ATP energy
  21. Genes located on the same chromosome and tending to be inherited together show the phenomenon ofaindependent assortmentbmutationclinkagedrecessiveness only
  22. In human beings (XX–XY system), the sex of the child is determined by theathe particular kind of egg that is producedbthe temperature at which incubation occurscthe general health and nutrition of the motherdtype of sperm (X- or Y-bearing) that fertilises the egg
  23. The role of messenger RNA (mRNA) in the cell is toacarry individual amino acids to the ribosomebform the structural core of the ribosomeccarry the coded message (codons) from DNA to the ribosomesdreplicate the DNA before cell division
  24. The parts of a gene that remain in the mature mRNA and are expressed are theaexonsbintronscpromotersdoperators
  25. During translation, amino acids are carried to the ribosome one by one byamRNA moleculesbribosomal RNAcsmall nuclear RNAdtransfer RNA (tRNA)
  26. A point mutation that changes one codon so that a different amino acid is inserted in the protein is aasilent mutationbnonsense mutationcframeshift mutationdmissense mutation
  27. Cork cells are impermeable to water because their walls are impregnated withasuberinblignin onlycpectindcutin of guard cells
  28. Normal secondary growth in thickness is absent in most monocot stems because their vascular bundles areawithout xylembclosed (without cambium)cwithout phloemdabsent altogether
  29. In a typical dorsiventral (dicot) leaf, stomata are generallyaonly on the upper surfacebmore numerous on the lower surfacecabsent from leavesdfound only on stems
  30. Temporary wilting of a plant on a hot afternoon occurs whenaabsorption exceeds transpirationbthe cells are fully turgidcguttation is at its maximumdtranspiration exceeds the absorption of water
  31. The upward movement of water in small herbs in the early morning, shown by guttation, is aided byaroot pressurebphotosynthesiscrespirationdphloem suction
  32. The products of the light reactions that are used up in the Calvin cycle (dark reactions) areaoxygen alonebglucose and watercATP and NADPHdcarbon dioxide
  33. The complete aerobic respiration of one glucose molecule yields, by modern estimates, abouta2 ATPb30–32 ATPc8 ATPd4 ATP
  34. Most of the carbon dioxide released in aerobic respiration is produced in theaglycolysis in the cytoplasmbCalvin cyclecKrebs cycle (and the link reaction)dphotolysis of water
  35. Bolting (rapid stem elongation) in rosette plants and breaking of seed dormancy are effects promoted byaabscisic acidbgibberellinscethylene onlydcytokinins only
  36. Pollination carried out by insects is technically termedaanemophilybhydrophilycornithophilydentomophily
  37. Parthenocarpy is the phenomenon of the development ofaseeds without fertilisationbmany embryos in one seedcfruit without fertilisation (seedless fruit)dseedlings on the mother plant
  38. A major advantage of micropropagation (tissue-culture propagation) of crop plants is the rapid production ofanew varieties every generationblarge numbers of identical, disease-free plantscplants without any growth hormonesdplants only in open fields
  39. Integrated pest management (IPM) for crop protection emphasisesaheavy, repeated use of a single chemical pesticidebpurely manual removal of every pest by hand-pickingcabandoning pest control and accepting crop lossesdcombined biological, cultural and need-based chemical methods
  40. An environmental concern raised about genetically modified (transgenic) crops is the possibility ofatransfer (flow) of the introduced genes to wild relativesbcomplete loss of yieldcinability of the crops to reproduce at alldevery GM food being poisonous

Chemistry (questions 81–130)

  1. The mass of 2 mol of calcium carbonate, CaCO₃ (molar mass 100 g/mol), isa100 gb200 gc50 gd20 g
  2. The number of molecules present in 9 g of water (0.5 mol) isa3.01 × 10²³b6.02 × 10²³c9.0 × 10²³d1.5 × 10²³
  3. The electron was discovered through cathode-ray experiments byaRutherfordbJ. J. ThomsoncNiels BohrdMillikan
  4. Rutherford's gold-foil (alpha-scattering) experiment led to the conclusion that the atomahas electrons in fixed circular orbits onlybis mostly empty space with a small, dense, positive nucleuscis a uniform plum-pudding spheredcontains neutrons in the outer region
  5. Elements placed in the same group of the periodic table show similar chemical properties because they have the same number ofaneutronsbelectron shellscprotonsdvalence electrons
  6. A coordinate (dative) covalent bond, in which both shared electrons come from one atom, is present in theaNaCl crystalbammonium ion, NH₄⁺chydrogen moleculedchlorine molecule
  7. Owing to its two lone pairs, the shape of the water molecule isalinearbbent (angular)cregular tetrahedraldtrigonal planar
  8. The oxidation number of manganese in KMnO₄ isa+2b+4c+7d+6
  9. A mixture of nitrogen and oxygen at a total pressure of 2 atm contains nitrogen with a mole fraction of 0.8. The partial pressure of nitrogen isa0.4 atmb1.6 atmc2.5 atmd0.8 atm
  10. A solution is made by dissolving 0.5 mol of a solute in 250 g of water. Its molality isa2 mol/kgb0.5 mol/kgc1 mol/kgd4 mol/kg
  11. If the equilibrium constant Kc of a reaction has a very large value, it means that at equilibrium the mixture consists mostly ofaalmost wholly the unchanged reactants onlybneither reactants nor products in the mixturecexactly equal amounts of reactants and productsdproducts (the reaction goes nearly to completion)
  12. An aqueous solution of ammonium chloride (salt of a strong acid and a weak base) isabasicbneutralcamphotericdacidic
  13. 10 mL of a 6 mol/L stock acid is diluted with water to a final volume of 250 mL. The concentration of the diluted acid isa0.6 mol/Lb0.24 mol/Lc2.4 mol/Ld0.024 mol/L
  14. The activation energy of a reaction may be described as theaenergy released by the productsbtotal energy of the productscminimum energy molecules need for an effective collisiondkinetic energy at room temperature
  15. A charge of 9650 C (0.1 mol of electrons) is passed through silver nitrate solution in electrolysis. The mass of silver deposited (Ag = 108) is abouta1.08 gb108 gc10.8 gd5.4 g
  16. Hess's law of constant heat summation states that the total enthalpy change for a reaction depends only on theainitial and final states, not on the path takenbthe number of steps followed along the pathcthe particular catalyst chosen for the reactiondthe physical state and material of the container
  17. Isobars are atoms of different elements that have the sameaatomic numberbmass numbercnumber of neutronsdnumber of electrons in their ions
  18. The allotrope of carbon used in pencils and as a solid lubricant isagraphitebdiamondccokedfullerene alone
  19. Hydrogen peroxide can act both as an oxidising agent and as a reducing agent because the oxidation state of its oxygen, lying between 0 and −2, isa−2b+2c−1d+1
  20. Ozone, O₃, is best described asaan allotrope of oxygenban oxide of hydrogencan isotope of oxygenda polymer of oxygen
  21. Moist chlorine bleaches vegetable colours permanently by the process ofareductionbdehydrationcoxidationdsubstitution
  22. The most abundant metal in the Earth's crust isaaluminiumbironccalciumdsodium
  23. "Blister copper" obtained in copper extraction owes its blistered appearance to the escape of the gasacarbon dioxidebhydrogencsulphur dioxidedsteam
  24. An alloy in which one of the components is mercury is known as anasolderbbrasscbronzedamalgam
  25. Liquation, in which the fusible metal melts and flows away from impurities, is used to purify a low-melting metal such asatinbironctungstendchromium
  26. Calcium ions in the body are essential, among other things, for the processes ofaoxygen transport in bloodbsynthesis of insulincnerve conduction by themselves alonedblood clotting and the formation of bones and teeth
  27. Excessive intake of which mineral element in the diet is most commonly linked with high blood pressure (hypertension)?aIronbIodinecSodiumdZinc
  28. Chlorine gas in bright sunlight breaks into chlorine atoms, Cl•, which then attack methane. These chlorine atoms, formed by equal splitting of the Cl–Cl bond, are examples ofacarbocationsbcarbanionscelectrophilesdfree radicals
  29. In the IUPAC system, the characteristic suffix used for ketones isa–alb–onec–oic acidd–ol
  30. A carbon atom joined to four different groups, giving rise to optical isomerism, is called an asymmetric (chiral) carbon. Optical activity thus requires the presence of aaa carbon–carbon double bond in the chainbcarbon with four different substituentsca plane of symmetry through the moleculeda benzene ring fused into the structure
  31. The chief component of natural gas (and of biogas) isapropanebbutanecethanedmethane
  32. In Markovnikov addition of HX to an unsymmetrical alkene, the hydrogen atom joins the carbon atom that already hasathe greater number of hydrogen atomsbthe smaller number of hydrogen atomsca halogen atom attacheddno substituents at all
  33. Benzene is aromatic in character because its ring carries a delocalised system ofa6 π-electrons (satisfying Hückel's 4n + 2 rule)b4 π-electrons in a fully conjugated ring systemc8 π-electrons delocalised around the whole ringdonly 2 π-electrons in an isolated double bond
  34. Freons, once widely used in refrigerators and now known to deplete the ozone layer, are chemicallyapure hydrocarbonsbmetal fluoridescchloroform alonedchlorofluorocarbons (CFCs)
  35. Methyl alcohol (methanol) is popularly known asawood spiritbgrain alcoholcrubbing alcoholdglycerine
  36. An unknown organic compound gives brisk effervescence (CO₂) with aqueous sodium hydrogencarbonate. The compound is most likely to be aaphenol dissolved in aqueous alkaliban alcohol such as ordinary ethanolccarboxylic acid such as benzoic aciddan ether such as methoxybenzene
  37. Glycerol (glycerine), propane-1,2,3-triol, is classed as aamonohydric alcoholbdihydric alcoholcphenoldtrihydric alcohol
  38. The characteristic smell of bitter almonds is due to the compoundageraniolbacetic acidchydrogen sulphidedbenzaldehyde
  39. Acid-catalysed hydrolysis of ethyl acetate yields the productsaethanol onlyba sodium salt onlycacetic acid and ethanoldmethane and carbon dioxide
  40. An ordinary soap (for example sodium stearate) is chemically the sodium salt of aastrong mineral acidbsugar acidchydrocarbondlong-chain fatty acid
  41. The first organic compound to be synthesised in the laboratory from an inorganic substance (Wohler, 1828) wasaglucosebacetic acidcureadbenzene
  42. Primary amines, when warmed with chloroform and alcoholic KOH, give a foul-smelling isocyanide. This test is called theacarbylamine reactionbTollens testcFehling testdLucas test
  43. Replacement of the diazonium group by chlorine using CuCl/HCl (or Cu/HCl) is known as theaSandmeyer reactionbWurtz reactioncKolbe reactiondCannizzaro reaction
  44. A Grignard reagent, much used in organic synthesis, has the general formulaaR–Li alwaysbR₂Zn onlycR–Mg–X (alkyl magnesium halide)d(C₂H₅)₄Pb
  45. DDT, whose use is now restricted because it persists and accumulates in food chains, is ananitrogenous fertiliserborganochlorine insecticidecweedicide onlydartificial vitamin
  46. Paracetamol, a very common medicine, acts in the body mainly as anaanalgesic and antipyretic (pain- and fever-reliever)ban antibiotic that kills disease bacteriacan antacid that neutralises stomach aciddan antiseptic applied directly to wounds
  47. Glass can be etched (frosted) and is attacked by the acidahydrochloric acidbsulphuric acidchydrofluoric acid (HF)dnitric acid
  48. Nessler's reagent turning brown is a sensitive test forachloride ionsbsulphate ionscferric ionsdammonia (ammonium ions)
  49. The brown-ring test, using FeSO₄ solution and concentrated H₂SO₄, is used to detect theachloride ionbnitrate ioncsulphide iondcarbonate ion
  50. On a paper chromatogram the solvent front has moved 9.0 cm while a coloured spot has moved 4.5 cm from the origin. The Rf value of the spot isa2.0b0.50c0.45d4.5

Physics (questions 131–180)

  1. The velocity of a body increases uniformly from 0 to 20 m/s in 5 s (a straight velocity–time graph through the origin). The distance travelled in these 5 s, given by the area under the graph, isa100 mb50 mc20 md200 m
  2. A star is 4 light years away. Taking the speed of light as 3 × 10⁸ m/s and 1 year ≈ 3.15 × 10⁷ s, the distance of the star is abouta3.8 × 10¹⁶ mb9.5 × 10¹⁵ mc3.8 × 10¹² md1.5 × 10¹⁷ m
  3. The recoil of a gun when a bullet is fired is explained by the law of conservation ofaenergy alonebmassclinear momentumdangular momentum
  4. A car of mass 1500 kg travels at 20 m/s. Its kinetic energy isa1.5 × 10⁵ Jb3 × 10⁵ Jc6 × 10⁵ Jd3 × 10⁴ J
  5. A thin ring of mass 2 kg and radius 0.5 m rotates about an axis through its centre perpendicular to its plane. Its moment of inertia (I = MR² for a ring) isa0.5 kg m²b1.0 kg m²c0.25 kg m²d2.0 kg m²
  6. Small raindrops are nearly spherical in shape because of the property of liquids calledathe viscosity of the water in the dropbcapillarity acting within the tiny dropcsurface tension (which minimises the surface area)dthe elasticity of the surface of the drop
  7. A mass of 0.25 kg hangs on a spring of force constant 100 N/m and oscillates vertically. The time period of oscillation is abouta0.31 sb3.1 sc1.3 sd0.05 s
  8. In uniform circular motion the velocity of the body is not constant, even though the speed is, becauseathe direction of motion changes continuouslybthere is no accelerationcthe speed keeps increasingdthe force is tangential
  9. A planet orbits the Sun at a mean distance of 4 AU (1 AU = Earth's distance). By Kepler's third law (T² ∝ a³), its orbital period isa2 yearsb4 yearsc16 yearsd8 years
  10. The unit of stress in the SI system, the same as that of pressure, is theanewtonbpascalcjouleddimensionless ratio
  11. 200 g of water at 90 °C is mixed with 300 g of water at 10 °C. Neglecting losses, the final temperature isa42 °Cb50 °Cc58 °Cd36 °C
  12. The silvered (shining) walls of a thermos flask reduce the transfer of heat chiefly byaconductionbconvectioncradiation (reflection)devaporation
  13. A clinical thermometer used for measuring body temperature usually has the range of abouta0 °C to 100 °Cb10 °C to 100 °Cc0 °C to 42 °Cd35 °C to 42 °C
  14. Burns caused by steam at 100 °C are more severe than those caused by the same mass of boiling water because the steam, on condensing on the skin,asteam is always far hotter than 100 °Cbsteam exerts a much greater pressure on skincsteam contains certain burning chemicalsdreleases its large latent heat of vaporisation as well
  15. The value of the universal gas constant R, in SI units, is abouta1.38 × 10⁻²³ J/Kb8.31 J mol⁻¹ K⁻¹c6.02 × 10²³ mol⁻¹d9.8 J mol⁻¹ K⁻¹
  16. A gas is taken round a rectangular cycle on a pressure–volume diagram: pressure between 1 × 10⁵ Pa and 3 × 10⁵ Pa, volume between 0.01 m³ and 0.03 m³. The net work done per cycle (the area enclosed) isa2000 Jb6000 Jc4000 Jd40 J
  17. In an isobaric process undergone by a gas, the quantity that is kept constant is theavolumebtemperaturecpressuredheat content
  18. Transverse mechanical waves (with the medium vibrating at right angles to the direction of travel) can propagate throughaa vacuumbthe bulk of a gascthe deep interior of a liquiddsolids (and along liquid surfaces)
  19. Waves travel at 100 m/s along a stretched string of length 0.5 m fixed at both ends. The fundamental (lowest) frequency of the string isa100 Hzb50 Hzc200 Hzd25 Hz
  20. An aircraft is said to be flying supersonically when its speed isagreater than the speed of sound in airbless than the speed of soundcequal to the speed of lightdexactly 340 m/s always
  21. Light travels at 2.0 × 10⁸ m/s in a block of glass (speed in vacuum 3.0 × 10⁸ m/s). The refractive index of the glass isa0.67b1.0c2.0d1.5
  22. Signals are carried along an optical fibre, from one end to the other without much loss, by the phenomenon of repeatedadiffractionbpolarisationctotal internal reflectiondscattering
  23. A hand magnifier (simple microscope) uses a convex lens with the object placedabeyond twice the focal lengthbat the centre of curvaturecat infinitydwithin (inside) its focal length
  24. Light of wavelength 600 nm passes through a single slit of width 0.1 mm. The angular position of the first diffraction minimum (sinθ ≈ θ = λ/a) is abouta0.06 radb0.006 radc0.6 radd6 rad
  25. For glass of refractive index 1.5, the Brewster (polarising) angle, given by tanθ = μ, is abouta34°b45°c42°d56°
  26. A wire of resistance 10 Ω is stretched uniformly to double its length (volume remaining constant). Its new resistance becomesa20 Ωb10 Ωc40 Ωd5 Ω
  27. To measure the current through a resistor, an ammeter is connectedain parallel with it, having high resistancebin series with it, having low resistancecin parallel with it, having low resistancedacross the battery only
  28. A galvanometer of resistance 100 Ω gives full-scale deflection at 1 mA. To convert it into a voltmeter reading up to 10 V, the resistance to connect isa9900 Ω in seriesb10,000 Ω in parallelc100 Ω in seriesd9900 Ω in parallel
  29. Outside a bar magnet, the magnetic field lines are conventionally drawn as emerging from theasouth pole and entering the north polebmiddle of the magnetcnorth pole and entering the south poledboth poles towards the middle
  30. A proton (charge 1.6 × 10⁻¹⁹ C) moves at 10⁶ m/s perpendicular to a magnetic field of 0.5 T (no electric field). The magnetic (Lorentz) force on it isa8 × 10⁻¹⁴ Nb8 × 10⁻¹³ Nc1.6 × 10⁻¹³ Ndzero
  31. To keep hysteresis loss small, the core of a transformer is made of a material such as soft iron, which has aaa wide hysteresis loop of very large areabnarrow hysteresis loop with low coercivitycstrong, permanent magnetism retained foreverdzero permeability to the magnetic field
  32. The magnetic flux through each turn of a 200-turn coil changes by 0.01 Wb in 0.1 s. The magnitude of the e.m.f. induced in the coil isa20 Vb2 Vc200 Vd0.2 V
  33. A pure capacitor (condenser) connected to a steady d.c. supply, after the initial charging moment,apasses a steady direct current indefinitelybblocks the direct current (acts as an open circuit)cacts exactly like a short circuit in the linedamplifies the direct current passing through
  34. An a.c. device draws an rms current of 2 A from a 220 V supply with a power factor of 0.5. The average power it consumes isa440 Wb110 Wc220 Wdzero
  35. A closed surface encloses a charge of 1.77 × 10⁻¹¹ C. Taking ε₀ = 8.85 × 10⁻¹², the total electric flux through the surface by Gauss's law isa0.5 N m²/Cb1.0 N m²/Cc4.0 N m²/Cd2.0 N m²/C
  36. When several capacitors are connected in series across a supply, the quantity that is the same on every capacitor is theapotential differencebenergy storedcmagnitude of the chargedcapacitance
  37. A lightning conductor fitted on a tall building protects it byaattracting the rain-clouds awaybproviding an easy, safe path for the discharge to the earthcpreventing clouds from formingdinsulating the building completely
  38. The electric field between two large, oppositely charged parallel metal plates (away from the edges) isaradial in characterbzero everywherecdecreasing as the inverse square of distanceduniform
  39. J. J. Thomson's experiments with cathode rays gave the value of the electron'sacharge alonebmass aloneccharge-to-mass ratio (e/m)dwavelength
  40. Light of wavelength 300 nm falls on a metal of work function 1.9 eV (hc = 1240 eV·nm). The stopping potential needed to halt the fastest photoelectrons is abouta4.1 Vb1.9 Vc2.2 Vd6.0 V
  41. The wave nature of moving electrons, predicted by de Broglie, was confirmed experimentally by the phenomenon ofascattering of alpha particlesbthe oil-drop experimentcthe photoelectric effectddiffraction of electrons by crystals
  42. The discrete (line) spectrum of the hydrogen atom is explained, in the Bohr theory, as arising fromathe vibration of atoms packed in a solidbcontinuous heating of the gas to high temperaturecthe rotation of the nucleus within the atomdtransitions of the electron between definite energy levels
  43. The characteristic X-rays emitted by the target of an X-ray tube are produced when the bombarding electrons cause, in the target atoms,atransitions involving the inner electron shellsbradioactive decay of the nucleictransitions in the outermost valence shelldheating of the filament
  44. A radioactive sample of mass 80 g has a half-life of 2 hours. The mass of the original isotope remaining after 8 hours isa10 gb5 gc20 gd2.5 g
  45. The binding energy per nucleon of nuclei is greatest (the nuclei most stable) for nuclei with mass numbersanear 56 (the iron region)bnear 1 (hydrogen)cnear 235 (uranium)dnear 4 only
  46. The fuel used in most nuclear power reactors to sustain the fission chain reaction is (enriched) uranium containing mainly the fissile isotopeauranium-238buranium-235cradium-226dthorium-232 alone
  47. A 6 V Zener diode is connected through a 600 Ω series resistor to a 12 V supply and operates in breakdown. The current through the resistor is abouta10 mAb20 mAc5 mAd30 mA
  48. The output of an exclusive-OR (XOR) gate is 1 (high) when its two inputs areaboth 0bboth 1cequal to each otherddifferent from each other
  49. In the quark model, a meson (such as the pion) is composed ofathree quarksba quark and an antiquarkctwo protonsdthree leptons
  50. Gravitational waves, predicted by Einstein a century earlier, were first detected directly in the year 2015 by the observatories calledathe Moon landingsbLIGO (from the merger of two black holes)cEinsteins own laboratory in 1915dthey have not been detected yet

Mental Agility Test (questions 181–200)

  1. Choose the word nearest in meaning to OBSOLETE.aBrand newbVery usefulcOutdated, no longer useddBroken
  2. Choose the word most opposite in meaning to PERMANENT.aEternalbStablecFixeddTemporary
  3. Tree : Forest :: Star : ?aSkybGalaxycPlanetdMoon
  4. Find the odd one out.aViolinbGuitarcFlutedSitar
  5. One word for "a person who writes books" isaauthorbeditorcpublisherdreader
  6. Find the next number in the series: 2, 3, 5, 7, 11, ?a12b15c13d17
  7. The square root of 144 isa14b12c16d18
  8. The fraction 3/5 expressed as a percentage isa30%b35%c50%d60%
  9. The perimeter of a square is 40 cm. Its area isa100 cm²b40 cm²c25 cm²d400 cm²
  10. Find the next number in the series: 100, 90, 81, 73, ?a65b66c64d67
  11. Statements: All cats are mammals. All mammals are warm-blooded. Which conclusion follows?aAll warm-blooded animals are catsbSome mammals are not warm-bloodedcAll cats are warm-bloodeddNo cat is warm-blooded
  12. If 1st January is a Monday in an ordinary (non-leap) year, 31st January of the same year falls on aaWednesdaybTuesdaycThursdaydMonday
  13. Find the next letter in the series: B, D, G, K, ?aMbNcOdP
  14. It is given that whenever it rains, the ground gets wet. The ground is observed to be wet. What can be concluded about rain?aIt certainly rained a short while agobIt has certainly not rained at all todaycOne cannot conclude that it rained (the wetness may have another cause)dThe ground in fact must really be dry
  15. C is taller than A. A is taller than B. D is the shortest of the four. Who is the tallest?aCbAcBdD
  16. The number of faces of a triangular prism isa4b5c6d8
  17. Which capital letter looks exactly the same in a plane mirror as it normally does?aJbIcLdF
  18. A man walks 10 m east, then 10 m south, then 10 m west, and finally 10 m north. How far is he from his starting point?a0 m (back at the start)b10 mc20 md40 m
  19. The (smaller) angle between the hands of a clock at exactly 6 o'clock isa90°b0°c120°d180°
  20. Which capital letter looks the same in its water image (reflection in a horizontal mirror below it)?aFbLcGdE

Answer key and explanations

Answers — Zoology (1–40)

1. (b) — Palaeontology studies fossil evidence of past life.

2. (b) — Chimpanzees share the most recent common ancestor with us.

3. (d) — Individuals are selected, but populations evolve.

4. (c) — Tracheae deliver air directly to insect tissues.

5. (c) — Reef corals are colonial cnidarian polyps with CaCO₃ skeletons.

6. (d) — Bats truly fly; the flying squirrel only glides.

7. (c) — The lancelet is a cephalochordate (no cranium, notochord throughout).

8. (d) — Every epithelium rests on a basement membrane.

9. (d) — Smooth (visceral) muscle lines hollow organs.

10. (a) — Gap junctions are communicating channels between cells.

11. (c) — Osteoblasts build bone; osteoclasts resorb it.

12. (b) — P. falciparum causes malignant tertian (cerebral) malaria.

13. (d) — Synchronous RBC rupture releases merozoites and haemozoin toxins.

14. (a) — Chloragogen cells store reserves like a liver.

15. (b) — The earthworm breathes through its moist skin (cutaneous respiration); once the skin dries, oxygen can no longer dissolve and diffuse in.

16. (d) — Fixed in front, the forked sticky tongue flips out backward to catch prey.

17. (d) — Buried in mud, the hibernating frog breathes cutaneously.

18. (a) — Parietal cells of the stomach secrete intrinsic factor.

19. (b) — Waves of smooth-muscle contraction propel the bolus.

20. (d) — Cooperative binding of the four subunits gives the S-curve.

21. (c) — Alveolar walls break down, shrinking the exchange surface.

22. (b) — The P wave is atrial depolarisation (contraction follows).

23. (a) — About 120 systolic / 80 diastolic mm Hg.

24. (b) — A single endothelial layer makes capillaries exchange vessels.

25. (d) — The proximal tubule recovers essentially all filtered glucose.

26. (d) — Henle's loops multiply the medullary osmotic gradient.

27. (a) — Oligodendrocytes myelinate CNS axons (Schwann cells serve the PNS).

28. (b) — They sense rotational acceleration for dynamic balance.

29. (c) — FSH is an anterior-pituitary (adenohypophyseal) hormone.

30. (c) — PTH raises plasma Ca²⁺ from bone, kidney and gut.

31. (a) — Ovulation occurs near mid-cycle, about day 14.

32. (c) — hCG from the early placenta maintains the corpus luteum (and is the pregnancy-test hormone).

33. (b) — Clostridium tetani toxin locks muscles in spasm.

34. (a) — Transferred antibodies protect at once but only briefly.

35. (c) — Destruction of spinal motor neurons paralyses the muscles they serve.

36. (b) — Leprosy is mycobacterial, like tuberculosis.

37. (a) — Foetal cells in the fluid are karyotyped for chromosomal disorders.

38. (a) — It substitutes for a faulty SA node with timed pulses.

39. (c) — Present needs met without stealing from the future.

40. (a) — Chitwan's Terai grasslands hold Nepal's rhino stronghold.

Answers — Botany (41–80)

41. (a) — Starch is a glucose polymer (amylose + amylopectin).

42. (d) — Vitamin C is ascorbic acid.

43. (b) — Tobacco mosaic is viral; the rest are fungal/oomycete diseases.

44. (c) — Lactobacillus ferments lactose to lactic acid, setting the curd.

45. (a) — Fungi store glycogen (and oils), like animals.

46. (b) — Puccinia graminis causes black stem rust of wheat.

47. (d) — Phycoerythrin masks the chlorophyll, giving the red colour.

48. (b) — Foot, seta and capsule make the moss sporophyte.

49. (a) — A sorus is a cluster of spore-producing sporangia.

50. (c) — Parallel veins are typical of monocot leaves.

51. (c) — The grass grain is a caryopsis with fused pericarp and seed coat.

52. (a) — One species, one area, interbreeding: a population.

53. (a) — Mutualism benefits both partners (e.g. legume + Rhizobium).

54. (d) — Stratospheric ozone screens out most solar UV.

55. (b) — Halophytes tolerate saline habitats.

56. (c) — Ribosomes are the protein factories.

57. (b) — Calcium pectate glues adjacent walls at the middle lamella.

58. (c) — Homologues pair (synapse) during zygotene.

59. (a) — Kinetochores at the centromere grip the spindle microtubules.

60. (d) — Movement against the concentration gradient that depends on respiratory energy is active transport; blocking ATP production stops it.

61. (c) — Linked genes travel together on one chromosome.

62. (d) — The sperm contributes either an X or a Y chromosome.

63. (c) — mRNA carries the codon sequence to be translated.

64. (a) — Exons are retained after splicing out the introns.

65. (d) — Each tRNA ferries its amino acid to the growing chain.

66. (d) — A missense change swaps one amino acid for another.

67. (a) — Suberised walls make cork waterproof and protective.

68. (b) — Closed bundles have no cambium for secondary thickening.

69. (b) — The shaded lower surface carries most stomata in dicot leaves.

70. (d) — Loss outrunning uptake drains cell turgor: wilting.

71. (a) — Root pressure pushes xylem sap up (seen as guttation).

72. (c) — ATP and NADPH from the thylakoids drive CO₂ fixation.

73. (b) — Current P/O ratios give ≈ 30–32 ATP per glucose (not the old 38).

74. (c) — Decarboxylations of the link reaction and Krebs cycle release the CO₂.

75. (b) — Gibberellins elongate stems and mobilise seed reserves.

76. (d) — Insect pollination is entomophily.

77. (c) — Parthenocarpic fruits (e.g. banana) form without fertilisation.

78. (b) — Tissue culture multiplies uniform, pathogen-free clones quickly.

79. (d) — IPM combines methods and minimises chemical pesticides.

80. (a) — Pollen-mediated gene flow to wild relatives is a key biosafety issue.

Answers — Chemistry (81–130)

81. (b) — 2 × 100 = 200 g.

82. (a) — 0.5 × 6.02 × 10²³ = 3.01 × 10²³ molecules.

83. (b) — Thomson identified cathode rays as electrons (1897).

84. (b) — Rare large deflections revealed a tiny, dense, positive nucleus.

85. (d) — Equal valence-electron counts give similar chemistry down a group.

86. (b) — In NH₄⁺ one N–H bond is dative (N donates both electrons to H⁺).

87. (b) — Two bonds and two lone pairs leave H₂O bent (≈ 104.5°).

88. (c) — +1 + x − 8 = 0 gives Mn = +7.

89. (b) — p(N₂) = mole fraction × total pressure = 0.8 × 2 = 1.6 atm (Dalton's law).

90. (a) — Molality = moles per kilogram of solvent = 0.5/0.250 = 2 mol/kg.

91. (d) — Large Kc means the equilibrium lies far to the products.

92. (d) — NH₄⁺ hydrolyses to give an acidic solution.

93. (b) — M₂ = M₁V₁/V₂ = 6 × 10/250 = 0.24 mol/L: dilution keeps the amount of solute unchanged.

94. (c) — Only collisions with at least the activation energy react.

95. (c) — Ag⁺ + e⁻ → Ag needs 1 mol of electrons per mole of silver: 0.1 mol × 108 = 10.8 g (Faraday's laws).

96. (a) — Hess's law: ΔH is path-independent.

97. (b) — Isobars share A but differ in Z.

98. (a) — Graphite's layers slide: pencil "lead" and lubricant.

99. (c) — Oxygen at −1 can rise to 0 or fall to −2.

100. (a) — O₃ is an allotropic form of oxygen.

101. (c) — Moist Cl₂ bleaches by oxidation (permanent, unlike SO₂).

102. (a) — Aluminium is the most plentiful crustal metal.

103. (c) — Escaping SO₂ blisters the solidifying copper.

104. (d) — Mercury alloys are amalgams.

105. (a) — Easily melted tin can be liquated away from infusible impurities.

106. (d) — Ca²⁺ is needed for clotting, bones and teeth.

107. (c) — High sodium (salt) intake is linked to hypertension.

108. (d) — Homolytic fission gives each fragment one electron of the pair: neutral, highly reactive free radicals that start chain reactions.

109. (b) — Ketones take the suffix –one (propanone, butanone).

110. (b) — Four different groups on one carbon destroy superposability.

111. (d) — Methane dominates natural gas and biogas.

112. (a) — Markovnikov: H goes to the carbon richer in H.

113. (a) — Six delocalised π electrons (n = 1 in 4n + 2).

114. (d) — Freons are chlorofluorocarbons.

115. (a) — Methanol from destructive distillation of wood: wood spirit.

116. (c) — Only acids stronger than carbonic acid decompose NaHCO₃; phenol is weaker than carbonic acid and gives no effervescence — a handy distinguishing test.

117. (d) — Three –OH groups make glycerol trihydric.

118. (d) — Benzaldehyde smells of bitter almonds.

119. (c) — Hydrolysis splits the ester back into acid + alcohol.

120. (d) — Soaps are Na/K salts of long-chain fatty acids.

121. (c) — Wöhler made urea from ammonium cyanate in 1828.

122. (a) — The isocyanide (carbylamine) stench identifies a 1° amine.

123. (a) — Sandmeyer: diazonium → aryl chloride/bromide with Cu(I) salts.

124. (c) — RMgX in dry ether is the Grignard reagent.

125. (b) — DDT is a persistent organochlorine insecticide.

126. (a) — Paracetamol relieves pain and reduces fever.

127. (c) — HF attacks silica, etching glass.

128. (d) — Nessler's reagent browns with ammonia/ammonium.

129. (b) — The brown [Fe(H₂O)₅NO]²⁺ ring signals nitrate.

130. (b) — Rf = distance moved by spot/distance moved by front = 4.5/9.0 = 0.50 (always between 0 and 1).

Answers — Physics (131–180)

131. (b) — Area of the triangle = ½ × 5 × 20 = 50 m (equivalently, mean speed 10 m/s × 5 s).

132. (a) — 4 × 3 × 10⁸ × 3.15 × 10⁷ ≈ 3.8 × 10¹⁶ m (one light year ≈ 9.5 × 10¹⁵ m).

133. (c) — Bullet and gun momenta are equal and opposite.

134. (b) — KE = ½ × 1500 × 20² = 300,000 J = 3 × 10⁵ J.

135. (a) — I = MR² = 2 × 0.25 = 0.5 kg m²: all the mass sits at the same distance R from the axis.

136. (c) — Surface tension pulls the drop to minimum area: a sphere.

137. (a) — T = 2π√(m/k) = 2π√(0.25/100) = 2π × 0.05 ≈ 0.31 s.

138. (a) — Velocity is a vector; turning changes it continually.

139. (d) — T² = 4³ = 64, so T = 8 years.

140. (b) — Stress (force/area) is measured in pascals.

141. (a) — Heat lost = heat gained: T = (200 × 90 + 300 × 10)/500 = 42 °C — closer to 10 °C because there is more cold water.

142. (c) — Shining walls reflect radiation back.

143. (d) — Clinical thermometers span roughly 35–42 °C.

144. (d) — Condensing steam dumps its latent heat into the skin too.

145. (b) — R ≈ 8.31 J mol⁻¹ K⁻¹.

146. (c) — Area = ΔP × ΔV = 2 × 10⁵ × 0.02 = 4000 J.

147. (c) — Isobaric = constant pressure.

148. (d) — Bulk fluids cannot sustain transverse (shear) waves; solids can.

149. (a) — The fundamental fits half a wavelength in 0.5 m, so λ = 1 m and f = v/λ = 100 Hz.

150. (a) — Supersonic = faster than sound (Mach > 1).

151. (d) — μ = c/v = 3.0/2.0 = 1.5.

152. (c) — Guided total internal reflection traps the light in the fibre.

153. (d) — Object inside f gives a virtual, erect, magnified image.

154. (b) — θ = 600 × 10⁻⁹/0.1 × 10⁻³ = 0.006 rad: a wide slit in wavelength terms gives a narrow central maximum.

155. (d) — tan⁻¹(1.5) ≈ 56°; at this angle the reflected light is completely plane-polarised.

156. (c) — L doubles and A halves, so R = ρL/A rises fourfold: 40 Ω.

157. (b) — An ammeter goes in series and must not resist the current it measures.

158. (a) — Total resistance needed = V/I = 10/0.001 = 10,000 Ω; subtract the coil's 100 Ω: 9900 Ω in series (a voltmeter must draw little current).

159. (c) — Field lines leave N and enter S outside the magnet.

160. (a) — F = qvB = 1.6 × 10⁻¹⁹ × 10⁶ × 0.5 = 8 × 10⁻¹⁴ N, perpendicular to both v and B.

161. (b) — Narrow loop, low coercivity: little energy lost per cycle.

162. (a) — e = N(ΔΦ/Δt) = 200 × 0.01/0.1 = 20 V (Faraday's law).

163. (b) — A charged capacitor stops steady d.c.

164. (c) — P = Vrms × Irms × cosφ = 220 × 2 × 0.5 = 220 W (the full 440 VA is only the apparent power).

165. (d) — Flux = Q/ε₀ = 1.77 × 10⁻¹¹/8.85 × 10⁻¹² = 2.0, independent of the surface's size or shape.

166. (c) — Series capacitors carry the same charge magnitude.

167. (b) — The rod conducts the stroke safely to the ground.

168. (d) — Between the plates the field is essentially uniform.

169. (c) — Thomson measured e/m of the cathode-ray particles.

170. (c) — Photon energy = 1240/300 = 4.13 eV; KEmax = 4.13 − 1.9 = 2.23 eV, so the stopping potential is about 2.2 V.

171. (d) — Davisson–Germer diffracted electrons from crystal surfaces.

172. (d) — Each line is a photon from a jump between allowed levels.

173. (a) — K/L-shell vacancies being filled emit characteristic X-rays.

174. (b) — 8 h = 4 half-lives: 80 × (½)⁴ = 5 g (the decayed portion has become other nuclides).

175. (a) — The binding-energy curve peaks near iron (A ≈ 56).

176. (b) — U-235 is the fissile fuel isotope.

177. (a) — The resistor drops 12 − 6 = 6 V, so I = 6/600 = 0.01 A = 10 mA; the Zener holds its terminal voltage near 6 V.

178. (d) — XOR is high only for unlike inputs.

179. (b) — Mesons are quark–antiquark pairs.

180. (b) — LIGO recorded GW150914, two black holes merging, in 2015.

Answers — Mental Agility Test (181–200)

181. (c) — Obsolete means out of date, no longer in use.

182. (d) — Temporary is the opposite of permanent.

183. (b) — Many trees form a forest; many stars form a galaxy.

184. (c) — The flute is a wind instrument; the others are stringed.

185. (a) — A writer of books is an author.

186. (c) — These are the prime numbers: next is 13.

187. (b) — 12 × 12 = 144.

188. (d) — 3/5 = 0.6 = 60%.

189. (a) — Side = 40/4 = 10 cm, area = 10² = 100 cm².

190. (b) — Subtract 10, 9, 8, then 7: 73 − 7 = 66.

191. (c) — Cats ⊆ mammals ⊆ warm-blooded.

192. (a) — 30 days later is 4 weeks + 2 days: Monday + 2 = Wednesday.

193. (d) — Gaps grow by one: +2, +3, +4, so +5 gives P.

194. (c) — Wet ground may come from other causes (a leaking pipe, dew, watering).

195. (a) — C > A > B and D shortest, so C is tallest.

196. (b) — Two triangular faces + three rectangular faces = 5.

197. (b) — I is symmetric left-to-right.

198. (a) — The four legs form a closed square.

199. (d) — At 6:00 the hands point in exactly opposite directions.

200. (d) — E is unchanged by a top-to-bottom flip.