General Science Questions and Answers

Answer: A

Among the galaxies listed, the Andromeda Galaxy is the nearest large galaxy to the Milky Way, at about 2.5 million light years. The Triangulum Galaxy is a little farther, at about 3 million light years, and the Sombrero and Whirlpool galaxies are much farther, at tens of millions of light years. Smaller dwarf galaxies such as the Large Magellanic Cloud are closer, but they are not offered, so Andromeda is the answer among the options.

The Large and Small Magellanic Clouds are about 160,000 and 200,000 light years away, which is why questions on the nearest galaxy name the choices.

Answer: C

Pluto is not included in the planet group. In 2006 the International Astronomical Union reclassified Pluto as a dwarf planet because it has not cleared its orbit of other bodies. Mars, Venus and Jupiter are among the eight planets of the solar system: Mars and Venus are terrestrial planets and Jupiter is a gas giant. So Pluto is the one that is not a planet. The IAU decision of 2006 defined a planet as a body that orbits the Sun, is nearly round and has cleared the neighbourhood around its orbit, and Pluto fails the last test, so it is classed as a dwarf planet. Mars, Venus and Jupiter pass all three tests.

Answer: D

Neil Armstrong and Buzz Aldrin landed on the Moon on 20 July 1969 during the Apollo 11 mission, so the year is 1969. Their landing and moonwalk showed a dry rocky surface of dust and rock with no water and no vegetation. 1965, 1966 and 1968 were years of earlier uncrewed or Earth-orbit missions, before the landing. The mission launched on 16 July 1969, the lunar module landed on 20 July, and the astronauts brought back samples that showed the surface to be dry, dusty basaltic rock. The other years in the options belong to the build-up of the Apollo programme, not to the landing.

Answer: C

Waste water treatment produces sludge and biogas as by-products: the sludge settles out and is treated, and the biogas, mostly methane, is produced when the sludge is digested without air, so statement I is correct. A septic tank is an on-site system for houses in places that have no sewerage system, so statement II is also correct. Both statements are right, and the answer is Both I and II, option (C). Here both of the statements describe real arrangements: the sludge is removed and digested, and the gas is collected and used as a fuel, and septic tanks serve scattered houses.

Answer: B

The correct matching is A-2, B-3, C-1, D-4.

• Gregor Mendel studied science at the University of Vienna before his pea experiments at Brno.
• Harold C. Urey, with Stanley Miller, carried out the 1953 experiment on the origin of organic molecules on the early earth.
• Charles Darwin's last book (1881) was on the role of earthworms in forming soil.
• Dmitri Mendeleev published the periodic table in 1869.

Mendeleev and the periodic table is the easy anchor, and Urey with the origin of life excludes the remaining options.

Answer: D

All four factors cause variation, so the answer is A, B, C and D.

The composition of milk, especially its fat and solids-not-fat content, varies with the stage of lactation (colostrum is very different from later milk, and fat rises again late in lactation), with the interval between milkings (a longer interval gives more milk with less fat), with environmental conditions such as temperature and season, and between individual animals even of the same breed and diet.

Feed, breed, age and disease such as mastitis also matter. Since all four listed factors contribute, the options naming only two or three of them are incomplete.

Answer: B

The calcium loss is due to microgravity.

On Earth, bones are constantly loaded by body weight, which stimulates bone formation. In the near-weightlessness of orbit that load disappears, so bone breaks down faster than it is rebuilt, especially in the weight-bearing bones of the legs, hips and spine. The calcium released from bone is excreted in the urine, which also raises the risk of kidney stones.

Astronauts counter it with daily resistance exercise. Hypergravity is the opposite condition, and diet or outside temperature are not the cause, since the astronauts live in a temperature-controlled cabin.

Answer: D

The pulmonary artery carries impure, deoxygenated blood - from the right ventricle to the lungs.

It is the one artery that does so; the pulmonary vein is likewise the one vein carrying oxygenated blood, from the lungs back to the left atrium. The rule that arteries carry pure blood fails for exactly this pair.

Answer: C

Calcium carbide reacts with water to give acetylene:

\[ \mathrm{CaC_2 + 2H_2O \rightarrow C_2H_2 + Ca(OH)_2} \]

The reaction was once used in carbide lamps, and acetylene burning in oxygen gives the 3,300°C flame used for welding and cutting steel.

Answer: D

Sodium is stored under kerosene. It reacts violently with water and even with the moisture in air, so it must be kept away from both.

Kerosene works because it is a hydrocarbon that does not react with sodium and is dense enough to keep the metal covered. Sodium in air quickly forms an oxide crust and can catch fire.