General Science MCQ Practice

• Insulin is an endocrine hormone secreted by the β-cells of the islets of Langerhans in the pancreas.
• It lowers blood glucose by helping cells absorb glucose and by promoting its storage as glycogen.
• Other organs listed do not secrete insulin: liver stores glucose, gall bladder stores bile, and kidneys filter blood and regulate minerals but do not release insulin.

• Malaria is caused by Plasmodium parasites (protozoan), transmitted by Anopheles mosquitoes, not a virus.
• Smallpox, AIDS (HIV), and Flu are viral diseases (virus causes infection or triggers disease).
• Key concept: viruses are distinct from parasites; malaria involves a parasite and a mosquito vector, not a viral pathogen.

Exam tip: If a disease involves a vector like a mosquito and a parasite, it is typically not viral.

• Correct reason: Apollo 11 landed on the Moon in 1969 (July 20, 1969). Neil Armstrong became the first man to walk on the lunar surface.
• Key concept: Lunar landing during the Earth–Moon travel mission sequence (Apollo program).
• Tip: Remember the famous line “one small step” from 1969.
• Why others are incorrect: 1967 and 1968 had orbital or unmanned tests, not a manned Moon landing; 1970 occurred after Apollo 11.

• Why: Burning of a candle is a chemical change. It involves a chemical reaction (combustion) with oxygen, forming new substances like carbon dioxide and water.
• Key concept: Chemical change → new substances with different properties; energy is often released as heat/light.
• Brief formula: Wax (hydrocarbons) + O2 → CO2 + H2O + energy.
• Why others are incorrect: Melting (B) and vaporization (C) are physical changes (change state, no new substance). Magnetising iron (D) mainly reorients domains (physical).
• Exam tip: Identify whether new substances are formed to distinguish chemical vs physical changes.

• Reason: Sound speed depends on the medium’s elasticity and density. In solids, bonds transmit vibrations faster. For steel, the elastic modulus is high and density is favorable, giving a high speed.
• Key concept: v ≈ √(E/ρ) for solids (longitudinal waves). Higher E and lower ρ (relative to E) yield higher v.
• Why others are incorrect: Vacuum has no medium for sound to travel; water and air are much less stiff, so their speeds are lower than steel.
• Exam tip: Remember: solids > liquids > gases; among solids, metals like steel are among the fastest.

• Concept: Aurorae occur where Earth's magnetic field is strongest at high latitudes. Charged solar particles collide with atmospheric gases, emitting light.
• Why A is correct: The Northern Hemisphere hosts the aurora borealis, a high-latitude phenomenon.
• Why not others: Equatorial regions lack the required magnetic-field interactions; Bermuda Triangle is unrelated; “None of these” is incorrect.
• Tip: Remember aurora borealis = Northern Hemisphere; aurora australis = Southern Hemisphere.

• Weight on a planet = mass × gravitational acceleration (W = m g).
• The Moon’s surface gravity is about 1.62 m/s², Earth’s is about 9.81 m/s², so gMoon ≈ 1/6 gEarth.
• Hence weight on the Moon ≈ (1/6) of Earth’s weight. This is the key concept: gravitational acceleration determines weight.

• Why others are incorrect:
• Air or water presence (A, B) does not affect weight.
• Option C states about half, which is false; actual is ~one-sixth.

• Why: Measles is caused by a virus — specifically the measles virus, an RNA virus in the family Paramyxoviridae (genus Morbillivirus).
• Key concept: Diseases are caused by different pathogens; measles is not bacterial, protozoan, or parasitic in origin.
• Wrong options: A. Bacteria – causes many diseases but not measles. B. Protozoa – causes malaria, amoebiasis, etc. C. Worm – causes helminth infections.

• Concept: A solar eclipse happens when the Moon comes between the Sun and the Earth and its shadow falls on Earth. This alignment occurs mainly during the new moon phase.
• Why D is correct: "Moon comes between the Sun and the Earth" places the lunar shadow on Earth, blocking sunlight.
• Key idea: The Moon’s apparent size must be similar to or larger than the Sun’s for total/partial solar eclipse to be visible.
• Why others are wrong: A and B describe Earth–Moon–Sun or Sun–Earth–Moon differently; C is about a right angle, not relevant to eclipses.
• Exam tip: Remember: solar eclipse = Moon in between Sun and Earth (new Moon phase).

• Why correct: The troposphere is the layer closest to Earth where most weather occurs, so it lies just above the surface.
• Key concept: Temperature generally decreases with height in the troposphere, and it contains the bulk of atmospheric mass.
• Other options:
  • Stratosphere, Mesosphere, Thermosphere are all higher layers above the troposphere.