Part-I MCQs: the 20 compulsory multiple-choice questions of the CSS 2024 General Science & Ability paper, with answers and short explanations.

Answers

1. In fish liver oil there is: (D) Vitamin A and Vitamin D. Cod liver oil is a classic source of both.

2. When are day and night equal? (B) 21st March and 23rd September, the approximate dates of the equinoxes.

3. Combinations of 9 things taken 3 at a time: (D) 84, as C(9, 3) = (9 × 8 × 7) ÷ (3 × 2 × 1) = 84.

4. The chemical formula for alum is: (A) KAl(SO₄)₂·12H₂O, potassium aluminium sulphate.

5. If the radius of a circle is increased three times, its area is increased: (C) Nine times, as area depends on r².

6. One degree of longitude on the equator is about: (B) 69 miles.

7. The protein molecule is made of: (D) Long range chain of amino acids.

8. The minimum amount of vitamin stored in the body is of: (B) Vitamin C. It is water-soluble, whereas A, D and E are fat-soluble and more readily stored.

9. The isotopes of any element contain equal numbers of: (A) Protons. This is what defines an element, and isotopes differ only in their neutrons. Neutral atoms also have equal electrons, but ions do not, so (C) is not always true.

10. The pH of soil is raised using: (A) Lime stone, which neutralises acidity.

11. Which of the following measures distance? (B) Light year, the distance light travels in a year.

12. Which has the most carbon atoms in one mole? (D) Ethanol, C₂H₅OH, with two carbon atoms per molecule.

13. A pencil dipped in water appears bent due to: (C) Refraction.

14. Fishes die outside water due to: (D) Non-absorption of oxygen, as their gills collapse and cannot work in air.

15. In dementia a person: (C) Loses thinking, remembering, and reasoning.

16. An earthquake is measured by: (C) Seismograph.

17. A cyclone is formed: (D) When warm, moist air rises upward over the ocean.

18. Why is red light used for danger? (D) It has long wavelength and short frequency. Its long wavelength scatters less, so it can be seen from far away. Here, 'short frequency' means low frequency.

19. Heavy water is: (C) Denoted by D₂O and contains deuterium.

20. The ionosphere extends: Not confirmed. Sources give different ranges, often from about 60 km up to several hundred kilometres or more, and no official key is published. Option (A), 60-300 km, is the closest of those given.