General Science Mixed Quiz: Set 52

The correct answer is B, 12 pairs. The cranial nerves arise from the brain and serve the head and neck, among them the optic nerve of sight, the auditory nerve of hearing, the olfactory nerve of smell and the vagus, which is the longest cranial nerve and reaches down to the heart, lungs and stomach. Option A is wrong because ten is the number in some lower vertebrates such as fishes and amphibians, which is why it is offered as a distractor. Option C is wrong because 31 pairs is the number of spinal nerves, which arise from the spinal cord, and the two figures must be kept apart: 12 cranial and 31 spinal. Option D is wrong because 33 is the number of vertebrae in the human vertebral column at birth, a different count altogether, fused later into 26 bones in an adult.

The correct answer is A, 1 and 4. Hooke's law holds only as far as the limit of proportionality, and that limit is either equal to or lower than the elastic limit, so statements 1 and 4 are the correct pair. Hooke's law says stress is proportional to strain, which is the straight part of the stress-strain graph; the point where the curve leaves the straight line is the limit of proportionality. A little beyond it the material still springs back to its original shape, and the last point at which it does so is the elastic limit. For most metals the two points lie very close together and for an ideal material they coincide. B is wrong because statement 2 extends the law past the straight part of the graph, where stress and strain are no longer proportional. C and D are wrong because statement 3 says always less, while the two limits may also be equal. Exam tip: order the four points as proportionality limit, elastic limit, yield point, ultimate stress.

The correct answer is C, cobalt. Vitamin B12 is chemically cyanocobalamin, and the cobalt atom at the centre of its ring is what the name points to; it is the only vitamin that contains a metal, it is absorbed only with the help of intrinsic factor secreted by the stomach, and its shortage gives pernicious anaemia. Option A is wrong because iron sits at the centre of haem in haemoglobin and in the cytochromes, not in a vitamin. Option B is wrong because magnesium is the metal at the centre of chlorophyll in green plants. Option D is wrong because zinc is a component of many enzymes, among them carbonic anhydrase, but not of any vitamin. B12 comes only from animal foods and microbial sources.

The correct answer is C, fish farming. Pisciculture is the rearing of fish in ponds, tanks and other managed waters, the Latin word piscis meaning fish. It is a branch of aquaculture and India is one of the largest fish producers in the world; the Blue Revolution is the name given to the planned growth of fish output, and rohu, catla and mrigal are the common Indian carps raised in ponds. A is wrong because the rearing of honey bees is apiculture, which gives honey and beeswax. B is wrong because the rearing of silkworms is sericulture, in which the mulberry-fed Bombyx mori gives most of the world's silk. D is wrong because the rearing of birds is aviculture, and the keeping of fowl for eggs and meat is poultry farming. Exam tip: learn the culture words together - pisciculture fish, apiculture bees, sericulture silkworms, aviculture birds, horticulture fruits and vegetables, floriculture flowers.

The correct answer is C, adrenaline, also called epinephrine, secreted by the medulla of the adrenal gland in fright, anger or stress. It quickens the heartbeat, raises the blood pressure, widens the air passages, sends more blood to the muscles and releases glucose from the liver, so that the body is ready to fight or to run. Option A is wrong because insulin lowers blood sugar and works in the quiet business of storing energy, the opposite of an emergency. Option B is wrong because thyroxine sets the long-term rate of metabolism and works over days and weeks, not seconds. Option D is wrong because oxytocin, from the posterior pituitary, causes the contraction of the uterus at childbirth and the ejection of milk, and is often called the birth hormone. The adrenal cortex, by contrast, makes cortisol for longer-term stress.

The correct answer is B, Galileo Galilei. Galileo was the first to argue that, with air resistance removed, every body falls with the same acceleration regardless of its mass. He reached this by rolling balls down inclined planes and timing them, and the idea is linked in popular accounts with his experiment from the Leaning Tower of Pisa. This overturned the older belief of Aristotle that heavier bodies fall faster. The acceleration he described is g, about 9.8 metres per second squared near the earth. A is wrong because Einstein built on this in the general theory of relativity through the equivalence principle, long afterwards. C is wrong because Edison was an inventor of the electric lamp and phonograph and did no work on falling bodies. D is wrong because Newton, born the year Galileo died, later explained why this happens through his law of gravitation. Exam tip: remember the order - Galileo found that all bodies fall alike, Newton explained the cause.

The correct answer is A, vitamin D. Vitamin D, chemically calciferol, is needed for the absorption of calcium and phosphorus from the intestine, so a child short of it cannot mineralise growing bone; the legs bow, the wrists thicken and the chest deforms, and the disease is rickets, while the same shortage in an adult softens formed bone as osteomalacia. It is called the sunshine vitamin because the skin makes it under ultraviolet light. Option B is wrong because a shortage of vitamin E causes the breakdown of red blood cells and, in animals, sterility. Option C is wrong because a shortage of vitamin B2 gives cheilosis and glossitis. Option D is wrong because a shortage of vitamin A affects the eye. Milk, egg yolk, fish liver oil and fortified foods supply vitamin D in the diet.

The correct answer is C, Cleaning. In electroplating the article to be coated is made the cathode, the plating metal serves as the anode, and both are dipped in an electrolyte containing a salt of that metal. When current flows, the metal ions travel to the cathode and settle on it. The coating can bond only if the surface is chemically clean, so grease, oil, rust and oxide are stripped off first by degreasing and by pickling in acid; any film left behind makes the plating peel, blister or come out patchy. Option A is wrong because buffing only brings up a shine on a surface that is already clean. Option B is wrong because soldering joins two metals with a filler alloy and has nothing to do with preparing a surface for plating. Option D is wrong because polishing smooths the surface mechanically but does not remove the oily and oxide films that spoil adhesion. Exam tip: the order is clean first, then plate, and the article is always the cathode.

The correct answer is C, the medulla oblongata, the lowest part of the brain stem, which joins the brain to the spinal cord and holds the centres for the heartbeat, for breathing and for the width of the blood vessels, as well as for vomiting, sneezing, coughing and swallowing. An injury here is fatal because these actions cannot be done at will. Option A is wrong because the cerebrum directs voluntary action and thought. Option B is wrong because the hypothalamus regulates body temperature, hunger, thirst and sleep and controls the pituitary, which is a related but different list, and a question may well test the difference. Option D is wrong because the cerebellum looks after balance and the coordination of movement. The three to fix are cerebrum for the voluntary, medulla for the involuntary and hypothalamus for the internal environment.

The correct answer is C, Thallophyta. Litmus is a purple dye taken from lichens, and in the classification used in school science lichens are placed in Thallophyta, the group of simple plants whose body is an undifferentiated thallus with no true root, stem or leaf. Algae and fungi belong to the same group, and a lichen is in fact a partnership of an alga and a fungus living together. Litmus is a natural indicator: it stays purple in a neutral solution, turns red in acid and blue in base, and is used both as a solution and as litmus paper. Option A is wrong because gymnosperms are well developed plants with naked seeds, such as pine and cycas. Option B is wrong because pteridophytes, the ferns, are the first plants with vascular tissue. Option D is wrong because bryophytes such as moss and Marchantia are called the amphibians of the plant kingdom. Exam tip: litmus is red in acid, blue in base and purple when neutral.

The correct answer is A, retinol. Retinol is vitamin A, and it is the raw material of rhodopsin, the pigment in the rod cells of the retina that lets us see in dim light; when it is short the eye cannot adjust to darkness, which is night blindness, and a longer shortage dries the conjunctiva as xerophthalmia and can destroy the cornea. Liver, milk and egg supply it ready made, and carrot and green leafy vegetables supply beta-carotene, which the body converts. Option B is wrong because calciferol is vitamin D, whose shortage gives rickets. Option C is wrong because tocopherol is vitamin E, an antioxidant. Option D is wrong because thiamine is vitamin B1, whose shortage gives beriberi. Night blindness is among the earliest signs of a vitamin A shortage and is reversible if treated in time.

The correct answer is C. Ultraviolet light is a transverse wave, not a longitudinal one, so this statement is the wrong one. In an electromagnetic wave the electric and magnetic fields vibrate at right angles to each other and to the direction the wave travels, which is the definition of a transverse wave. Longitudinal waves need a material to squeeze and stretch, and sound is the standard example. Option A is correct because ultraviolet light sits in the electromagnetic spectrum between visible light and X-rays. Option B is correct because electromagnetic waves need no medium and cross empty space, which is how the Sun's ultraviolet rays reach the earth. Option D is correct because ultraviolet wavelengths run from about 400 nanometres down to 10 nanometres, shorter than violet light, and this higher energy is what burns skin and is absorbed by the ozone layer. Exam tip: all electromagnetic waves are transverse; only mechanical waves such as sound can be longitudinal.

The correct answer is C, the sciatic nerve, which is also the thickest nerve in the body. It is formed from the roots of the lower spine, passes through the buttock and runs down the back of the thigh to the leg and foot, and its compression by a slipped disc causes the pain called sciatica. Option A is wrong because the vagus, the tenth cranial nerve, is the longest of the cranial nerves and travels from the brain to the heart, lungs and gut, but it is shorter than the sciatic; the two records are often confused, so remember sciatic for the body and vagus for the cranial nerves. Option B is wrong because the optic nerve is short, carrying impulses from the retina to the brain. Option D is wrong because the trigeminal, the largest cranial nerve by thickness, serves the face and the muscles of chewing.

The correct answer is C, Red color scatters less than other colors. At sunset the Sun is close to the horizon, so its light travels through a much thicker layer of atmosphere before it reaches the eye. Air molecules scatter short wavelengths, blue and violet, far more strongly than long ones; this is Rayleigh scattering, in which the scattering falls off as the fourth power of the wavelength. Over that long slanting path almost all the blue is scattered sideways out of the beam, and mostly the long-wavelength red and orange light survives to reach us, so the Sun and the sky around it look red. Option A is wrong because sunlight is white and contains all seven colours. Option B is wrong because red is scattered the least, not the most; blue is scattered most, which is why the midday sky is blue. Option D is wrong because the effect lies in the atmosphere, not in the sensitivity of the eye. Exam tip: Rayleigh scattering gives a blue sky at noon and a red Sun at sunrise and sunset.

The correct answer is B, A, D, E and K. These four dissolve in fat and not in water, so they travel with dietary fat, are stored in the liver and in body fat, show their deficiency only after a long shortage, and can be toxic in excess. The B complex vitamins and vitamin C are water soluble; the body cannot store them, the surplus is passed out in urine and they are easily lost in cooking water. Options A, C and D are wrong because each of them includes B or C, or both, among the fat soluble group. A simple way to remember the four is the word DAKE, or to note that they are the vitamins a person deficient in bile or fat absorption is likely to lack.

The correct answer is C, a mechanism to reduce CO2 emission. A nuclear reactor splits heavy atoms; it burns no fuel, so it releases no carbon dioxide and needs no equipment to cut such emissions. The heat of fission is produced in the reactor core, carried away by a coolant, passed to water in a heat exchanger or steam generator, and the steam then turns a turbine coupled to a generator. Control rods of cadmium or boron absorb spare neutrons and a moderator such as heavy water slows them down so that fission continues steadily. Option A is wrong as a choice because the turbine is the part that actually converts steam energy into electricity. Option B is wrong because the heat exchanger carries heat from the radioactive coolant loop to the clean water loop. Option D is wrong because the reaction chamber, the core holding the fuel rods, is where fission happens. Exam tip: a nuclear plant emits no carbon dioxide; its waste problem is spent radioactive fuel instead.

The correct answer is B, protein. Kwashiorkor appears when a child gets enough calories but far too little protein, typically after being weaned onto a starchy gruel; the signs are swelling of the feet and face, a distended belly, thin and discoloured hair and an apathetic look, while the muscles are not severely wasted. Option A is wrong because a shortage of calories along with protein gives marasmus instead, in which the child is extremely wasted and looks old. Option C is wrong because an iron shortage gives anaemia, with pallor and tiredness. Option D is wrong because an iodine shortage gives goitre and, in a young child, cretinism. Kwashiorkor and marasmus together are called protein energy malnutrition. Pulses, milk, egg and soya are the cheap protein sources used to treat and prevent it.

The correct answer is B, are long chain molecules held together by secondary bonds. In a thermoplastic the polymer exists as long linear or lightly branched chains, and one chain is held to the next only by weak secondary forces such as van der Waals attraction. Heat gives enough energy to loosen those weak links, so the material softens, can be moulded into a new shape and hardens again on cooling, and the cycle can be repeated, which is why thermoplastic waste is recyclable. Polyethylene, polypropylene, PVC, polystyrene and nylon all belong to this group. A is wrong because a three-dimensional network of strong primary bonds describes a thermosetting plastic such as bakelite, which sets once and cannot be remoulded. C is wrong because the ability to deform plastically rises with temperature instead of falling. D is wrong because the secondary bonds do break as thermal energy rises, and that is exactly why the plastic softens. Exam tip: thermoplastic means weak secondary bonds and remoulding, thermosetting means cross-linked primary bonds and a shape set for good.

The correct answer is C, iodine. Iodine is needed to make thyroxine, the hormone of the thyroid gland; when the supply is short the gland works harder and enlarges into the swelling at the front of the neck called goitre, and in an infant the same shortage stunts growth and mental development as cretinism. This is why the law requires common salt to be iodised. Option A is wrong because an iron shortage gives anaemia. Option B is wrong because a calcium shortage weakens bone and teeth and disturbs clotting and muscle action. Option D is wrong because fluorine is the mineral whose shortage gives dental caries, while its excess in drinking water gives fluorosis, mottling teeth and deforming bone. Iodine deficiency disorders are the commonest preventable cause of mental impairment in the world.

The correct answer is C, fat. A gram of fat yields about nine kilocalories, more than twice the yield of carbohydrate or protein, because its carbon chains are far less oxidised to begin with; this is also why fat is the body’s store of energy and why fatty food is called energy dense. Options A and B are wrong because carbohydrate and protein each yield about four kilocalories per gram, and protein is in any case used mainly for building and repair rather than for fuel. Option D is wrong because vitamins yield no energy at all; they are needed in milligram quantities as coenzymes and regulators, and a vitamin tablet cannot replace a meal. Water and dietary fibre likewise yield no calories, though both are necessary in the diet.