UPSC Previous Year GK Questions with Answers

The correct answer is B, 2 and 3 only. Rakhmabai had been married as a child and refused to join her husband's household as an adult; he went to court for the restitution of conjugal rights, so statement 3 is part of the case. The judgment and the uproar that followed turned on whether a girl married as a child could be compelled to cohabit, and the campaign it fuelled produced the Age of Consent Act of 1891, which raised the age from ten to twelve years, so statement 2 is also part of it. Statement 1 is not: although Rakhmabai later studied medicine in England and became one of India's first practising woman doctors, the litigation itself was not about a right to education, which is why options A, C and D, each of which includes statement 1, are wrong.

The correct answer is D, vacuoles full of cell sap. A large central vacuole filled with sap presses the cytoplasm against the cell wall, keeping the cell firm, or turgid.

In a mature plant cell the central vacuole can take up 50 to 90% of the cell's volume. Its membrane, the tonoplast, controls what enters it, and the sap holds water, sugars, salts, pigments and wastes. When the vacuole is full, water pressure inside pushes outward on the wall; this turgor pressure keeps leaves spread out and soft stems upright. When the plant loses water, vacuoles shrink and the plant wilts.

A is wrong: ribosomes are tiny particles that make proteins; they give no shape or firmness.

B is wrong: mitochondria release energy through respiration; they are not concerned with turgidity.

C is wrong: the Golgi apparatus packages and secretes materials, including those for the cell wall, but it does not keep the cell turgid.

Exam tip: turgidity = central vacuole (turgor pressure); its membrane = tonoplast; animal cells have small or no vacuoles.

The correct answer is D, Annelida. Annelids such as the earthworm, leech and Nereis are the first coelomates in the usual sequence: their body cavity is lined on all sides by mesoderm.

Zoologists group animals by their body cavity. Acoelomates have no cavity at all; pseudocoelomates, such as roundworms (Aschelminthes), have a cavity only partly lined by mesoderm; true coelomates have a cavity fully lined by mesoderm, which gives room for organs to grow and move. Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata and Chordata are all coelomates. In the earthworm, the fluid in this coelom also acts as a hydrostatic skeleton for burrowing.

A is wrong: Porifera, the sponges, are at the cellular level of organisation and have no true tissues or coelom.

B is wrong: Platyhelminthes, the flatworms such as tapeworm and liver fluke, are acoelomate.

C is wrong: Cnidaria such as Hydra and jellyfish are diploblastic, with only a gut cavity and no coelom.

Exam tip: acoelomate = flatworms; pseudocoelomate = roundworms; coelomate starts with Annelida.

The correct answer is D, Methanol. No pathway of respiration in living cells turns glucose into methanol.

Glucose is first split in the cytoplasm into two molecules of pyruvate; this step, glycolysis, is common to all cells. What follows depends on oxygen. With oxygen, pyruvate is broken down in the mitochondria to carbon dioxide and water, releasing the most energy. Without oxygen, yeast converts pyruvate to ethanol and carbon dioxide, the basis of brewing and bread making, while our muscle cells during hard exercise convert it to lactic acid, which causes cramps.

A is wrong: ethanol is the product of anaerobic respiration (fermentation) in yeast.

B is wrong: lactic acid forms in muscle cells and in lactic acid bacteria when oxygen is short.

C is wrong: water, with carbon dioxide, is the end product of aerobic respiration.

Exam tip: glucose → pyruvate (cytoplasm) → CO2 + H2O (with oxygen), ethanol + CO2 (yeast), lactic acid (muscle).

The correct answer is D, Oxygen. Of the four options, oxygen is by far the most plentiful element; it makes up about 46% of the Earth's crust by mass.

Oxygen is locked in rocks as silicates and oxides, makes up about 89% of the mass of water and about 21% of the air by volume. The order of elements in the crust is oxygen, silicon, aluminium, iron, calcium, sodium, potassium and magnesium. If the whole planet is counted, iron, concentrated in the core, rivals oxygen, but iron is not among the options here.

A is wrong: silicon is second in the crust, about 28%, mostly combined with oxygen in silica and silicates.

B is wrong: aluminium is third in the crust, about 8%, and the most abundant metal there.

C is wrong: carbon, though the basis of all life, is only a tiny fraction of the Earth's crust.

Exam tip: crust order O > Si > Al > Fe; most abundant metal in the crust = aluminium; most abundant gas in air = nitrogen.

The correct answer is B. The melting point is the minimum temperature at which a solid melts to become a liquid at atmospheric pressure, not the maximum.

At the melting point the particles have just enough energy to overcome the forces holding them in fixed places. Ice melts at 0°C (273 K), and the temperature stays there until all of it has melted, because the heat supplied goes into breaking the arrangement; this hidden heat is the latent heat of fusion. Calling it the maximum temperature is the error the paper setter planted.

A is correct: heating a solid makes its particles vibrate faster, so their kinetic energy rises.

C is correct: steam at 100°C holds the extra latent heat of vaporisation (about 2260 kJ per kg), which is why a steam burn is worse than a burn from boiling water.

D is correct: a gas turning straight into a solid, as frost forms from water vapour, is deposition; the reverse is sublimation.

Exam tip: melting point = minimum temperature for melting; ice 0°C; steam at 100°C carries more energy than water at 100°C.

The correct answer is B, 1, 2 and 4. For small swings the time period is T = 2π√(L/g), which contains the length and gravity but neither the mass nor the amplitude.

Statement 1 is correct: T grows with the square root of length, so a pendulum four times longer takes twice as long per swing. Statement 2 is correct: T falls as g rises, so a pendulum clock runs slow on a hill or on the Moon, where g is smaller. Statement 3 is wrong: the mass of the bob cancels out of the equation, so a heavy and a light bob on equal strings swing together. Statement 4 is correct: for small amplitudes the period is the same however wide the swing, which Galileo noticed and which makes pendulum clocks possible.

A is wrong: it includes statement 3 and leaves out statement 4.

C is wrong: it includes the wrong statement 3 and drops statement 1.

D is wrong: it drops statement 2, though g appears in the formula.

Exam tip: T = 2π√(L/g); independent of mass and (small) amplitude; seconds pendulum ≈ 1 m long, T = 2 s.

The correct answer is C, apical meristem. Apical meristem sits at the growing tips of stems and roots, and its dividing cells make them longer.

Meristems are groups of cells that keep dividing throughout a plant's life. The shoot apex and root apex hold apical meristems, so a plant grows in length from its tips; this is primary growth. In the root the tip is shielded by a root cap as it pushes through soil. Lateral meristem (vascular cambium and cork cambium) adds girth instead, and intercalary meristem lengthens internodes and leaf bases in grasses and bamboo.

A is wrong: lateral meristem increases the thickness of stems and roots, not their length.

B is wrong: intercalary meristem works at the base of internodes and leaves, mainly in grasses; it does not lengthen roots.

D is wrong: secondary growth, by cambium, increases girth; growth in length is primary growth.

Exam tip: apical = length (tips); lateral = girth (cambium); intercalary = base of internodes (grasses, regrowth after grazing).

The correct answer is C, Polyaromatic hydrocarbons. Polyaromatic hydrocarbons are soot-related pollutants from incomplete burning; they are not among the gases that make up photochemical smog.

Photochemical smog forms on warm, sunny days in cities with heavy traffic. Vehicle exhaust releases nitric oxide and unburnt hydrocarbons; nitric oxide turns into nitrogen dioxide, which sunlight splits to free oxygen atoms that make ozone. Ozone and nitrogen oxides then react with hydrocarbons to form peroxyacetyl nitrate (PAN), formaldehyde and acrolein. The mix irritates the eyes and lungs and damages plants. It is oxidising, unlike the reducing classical smog of smoke and sulphur dioxide seen in London.

A is wrong: ozone is the main oxidant in photochemical smog.

B is wrong: PAN is a typical secondary pollutant of photochemical smog and a strong eye irritant.

D is wrong: nitric oxide from vehicle engines is the starting point of the smog reactions.

Exam tip: photochemical smog = NO, NO2, O3, PAN, aldehydes (oxidising, Los Angeles type); classical smog = smoke + SO2 (reducing, London type).

The correct answer is C, HIV-AIDS. HIV spreads through body fluids such as blood, semen, vaginal fluid and breast milk, not through droplets from coughing, sneezing or talking.

The human immunodeficiency virus attacks helper T cells and weakens the immune system; AIDS is its late stage. It passes on through unprotected sexual contact, transfusion of infected blood, shared needles and syringes, and from an infected mother to her child during pregnancy, birth or breastfeeding. It does not spread by shaking hands, sharing food, hugging or breathing the same air.

A is wrong: the bacteria and viruses that cause pneumonia spread through droplets from the nose and mouth.

B is wrong: COVID-19, caused by the SARS-CoV-2 virus, spreads mainly by respiratory droplets and aerosols.

D is wrong: tuberculosis, caused by Mycobacterium tuberculosis, spreads when a patient with lung TB coughs or sneezes.

Exam tip: droplet diseases = TB, COVID-19, flu, pneumonia, common cold; HIV and hepatitis B = blood and body fluids.

The correct answer is B, 2-1-3-4. The operations fall in 1965, 1971, 1984 and 1999, in that order: Riddle, Cactus Lily, Meghdoot, Safed Sagar.

Operation Riddle was the Indian Army's thrust towards Lahore in September 1965, during the second India–Pakistan war. Operation Cactus Lily was the 1971 operation in the eastern theatre in which troops were airlifted across the Meghna river by helicopters, hastening the fall of Dhaka and the birth of Bangladesh. Operation Meghdoot, launched in April 1984, secured the Siachen Glacier. Operation Safed Sagar was the Indian Air Force's part in the 1999 Kargil war, alongside the Army's Operation Vijay.

A is wrong: it puts Cactus Lily (1971) before Riddle (1965).

C is wrong: it opens with Safed Sagar, the latest of the four (1999).

D is wrong: it also starts with Safed Sagar and places Meghdoot (1984) last.

Exam tip: Riddle 1965 → Cactus Lily 1971 → Meghdoot 1984 (Siachen) → Safed Sagar 1999 (IAF in Kargil).

The correct answer is B, Active transport of ions and small molecules across cell membrane against concentration gradient requires energy. Moving a substance from low to high concentration is uphill work, and the cell pays for it with ATP.

In active transport, carrier proteins called pumps in the membrane use energy from ATP to push ions such as K+ and nitrate into root hair cells, even when the soil holds far less of them than the cell does. Diffusion and osmosis, by contrast, are passive: substances move down their own gradient, from high to low concentration, without spending energy.

A is wrong: diffusion is passive and needs no energy from the cell.

C is wrong: moving anything against a concentration gradient always needs energy; the cell cannot do it for free.

D is wrong: plant cells do move ions across membranes all the time, through channels, carriers and pumps; that is how roots take up minerals.

Exam tip: down the gradient = diffusion or osmosis, no energy; up the gradient = active transport, needs ATP.

The correct answer is D, Ribosomes. Ribosomes stuck on the outer surface of the endoplasmic reticulum give it a grainy, rough look under the electron microscope.

The endoplasmic reticulum is a network of membrane tubes and sacs in the cytoplasm. The part carrying ribosomes is the rough ER, and it is busy making proteins, especially those to be secreted or placed in membranes. The part without ribosomes is the smooth ER, which makes lipids and steroid hormones and helps detoxify drugs in liver cells. Cells that secrete a lot of protein, such as pancreatic cells, have plenty of RER.

A is wrong: centrioles are paired cylinders near the nucleus that help in cell division; they are not on the ER.

B is wrong: plastids such as chloroplasts are large separate organelles of plant cells.

C is wrong: lysosomes are free membrane sacs of digestive enzymes, not particles fixed on the ER.

Exam tip: RER = ribosomes + protein synthesis; SER = no ribosomes + lipid synthesis and detoxification.

The correct answer is B, Ion-exchange. An ion-exchange resin or zeolite swaps the calcium and magnesium ions that cause permanent hardness for sodium or hydrogen ions.

Permanent hardness comes from the chlorides and sulphates of calcium and magnesium, which do not break down on heating. In the zeolite (permutit) process, sodium aluminium silicate takes up Ca2+ and Mg2+ and gives out Na+, which does not harden water; the exhausted zeolite is renewed by washing it with brine. Synthetic resins work the same way. Washing soda and Calgon also remove permanent hardness.

A is wrong: boiling removes only temporary hardness, by turning soluble bicarbonates into insoluble carbonates.

C is wrong: lime treatment, Clark's method, also removes only temporary (bicarbonate) hardness.

D is wrong: bubbling sulphur dioxide only makes the water acidic; it does not take out calcium or magnesium.

Exam tip: temporary hardness = bicarbonates, removed by boiling or Clark's lime; permanent = chlorides and sulphates, removed by washing soda, Calgon or ion exchange.

The correct answer is C, Smooth muscle. Smooth muscle is a muscular tissue, one of the four basic animal tissues, not a connective tissue.

Animal tissues are of four kinds: epithelial, connective, muscular and nervous. Connective tissues have cells spread in a matrix and bind or support other parts; they include bone, cartilage, blood, areolar tissue, adipose tissue, ligaments and tendons. Smooth muscle is made of spindle-shaped, unstriated cells that contract on their own, without our will, in the walls of the stomach, intestines, blood vessels and the iris.

A is wrong: a ligament is dense connective tissue joining bone to bone; it is strong and elastic.

B is wrong: a tendon is dense connective tissue joining muscle to bone; it is strong but has little elasticity.

D is wrong: cartilage is a connective tissue with a firm matrix, found in the nose, ear, trachea and joint surfaces.

Exam tip: ligament = bone to bone, tendon = muscle to bone; muscles (smooth, skeletal, cardiac) are a separate tissue.

The correct answer is A, Cu(I) and S of Cu2S. Copper in the +1 state is reduced to metal, so it is the oxidant; sulphur of Cu2S is oxidised, so it is the reductant.

Track the oxidation numbers. Copper goes from +1 in both Cu2O and Cu2S to 0 in metallic Cu: it gains electrons, is reduced, and therefore acts as the oxidising agent. Sulphur goes from −2 in Cu2S to +4 in SO2: it loses six electrons, is oxidised, and therefore acts as the reducing agent. Oxygen stays at −2 throughout. This self-reduction is the last step in extracting copper from copper glance in a Bessemer converter.

B is wrong: metallic Cu and the S of SO2 are products, not the species that cause the change.

C is wrong: oxygen keeps the same oxidation number, so it is neither oxidant nor reductant.

D is wrong: Cu(I) is the oxidant, but oxygen is not the reductant; sulphur is.

Exam tip: oxidant gets reduced (oxidation number falls); reductant gets oxidised (number rises).

The correct answer is C, The summer solstice occurs in northern hemisphere on June 21 and on December 21 in southern hemisphere. The two hemispheres always have opposite seasons, so one hemisphere's summer solstice is the other's winter solstice.

On about 21 June the Sun is overhead at the Tropic of Cancer; the northern hemisphere has its longest day and summer begins there, while the southern hemisphere has its shortest day. On about 22 December the Sun is overhead at the Tropic of Capricorn, and the roles reverse: Australia and Argentina have their summer solstice. The cause is the Earth's axis, tilted at about 23.5°.

A is wrong: 21 June is winter solstice only in the southern hemisphere, not in both.

B is wrong: December 21 is winter solstice only in the northern hemisphere.

D is wrong: it swaps the dates; the northern summer solstice is in June, not December.

Exam tip: 21 June = Sun over Tropic of Cancer (northern summer); 22 December = Tropic of Capricorn (southern summer).

The correct answer is B, Uttar Pradesh. The Ghatampur Thermal Power Project stands at Ghatampur in Kanpur Nagar district of Uttar Pradesh.

It is a coal-based plant of three units of 660 MW each, built by Neyveli Uttar Pradesh Power Limited, a joint venture of NLC India Limited and the Uttar Pradesh Rajya Vidyut Utpadan Nigam. It uses supercritical technology, which burns less coal for each unit of power, and most of its electricity goes to Uttar Pradesh. A paper setter links the place, Kanpur, with the state.

A is wrong: Bihar's large thermal plants include Barh, Kahalgaon and Nabinagar, not Ghatampur.

C is wrong: Madhya Pradesh is known for Vindhyachal, Satpura and Sasan, not Ghatampur.

D is wrong: Gujarat's big coal plants are at Mundra and Ukai; Ghatampur is not in Gujarat.

Exam tip: Ghatampur = Kanpur Nagar, Uttar Pradesh; a 3 × 660 MW NLC–UP joint venture.

The correct answer is C, Proteins in mammalian cells are synthesized in rough endoplasmic reticulum. The RER is studded with ribosomes, the actual sites where amino acids are joined into proteins.

Ribosomes read the message carried by mRNA and link amino acids in the right order. Those attached to the rough endoplasmic reticulum make proteins meant for membranes or for export, such as enzymes and hormones; the new chains enter the RER, fold, and then move on in vesicles. Free ribosomes in the cytoplasm make proteins used inside the cell.

A is wrong: the cell membrane only controls what enters and leaves; it has no protein-making machinery.

B is wrong: food proteins are digested into amino acids, which are absorbed and then built into the body's own proteins inside cells.

D is wrong: the Golgi apparatus modifies, packages and dispatches proteins made in the RER; it does not make them.

Exam tip: ribosome (on RER) = protein synthesis; Golgi = packaging and secretion; SER = lipid synthesis.

The correct answer is D, The cell will lose water. A medium more concentrated than the cell is hypertonic, so water leaves the cell by osmosis.

In osmosis water moves across a selectively permeable membrane from the side with fewer dissolved particles to the side with more. If the outside solution is stronger, water flows out and the cell shrinks; in a plant cell the cytoplasm pulls away from the wall, which is called plasmolysis. This is why salted raw mango pieces give out water and why sprinkling salt on a garden leech shrivels it.

A is wrong: a cell gains water only when the outside medium is weaker, that is hypotonic.

B is wrong: losing some water does not by itself kill the cell; a plasmolysed plant cell recovers when put back in water.

C is wrong: no net change happens only in an isotonic medium of equal concentration.

Exam tip: hypertonic outside = cell shrinks (plasmolysis); hypotonic outside = cell swells; isotonic = no change.