In which unit is India's area generally expressed?

Correct answer: Square kilometres

Option A is correct because area measures the amount of two-dimensional surface covered by a place, and its standard metric unit is the square metre. For large countries such as India, the more convenient unit is the square kilometre, written as km². One square kilometre equals the area of a square measuring one kilometre on each side, or 1,000 metres × 1,000 metres = 1,000,000 square metres. Litres measure volume, kilograms measure mass, and seconds measure time, so none of those units can express geographical area. The governing concept is matching a physical quantity with its correct unit. Since the question concerns the surface extent of a country rather than its weight, capacity or duration, square kilometres are appropriate. Therefore, option A is the only scientifically and geographically valid answer.