In South Asia, the country with the largest percentage of aged population is

The correct answer is D) Sri Lanka. Sri Lanka has the highest share of elderly people in South Asia. Its fertility fell to near-replacement or below early, and life expectancy is high, so its population began ageing well ahead of its neighbours.

• Bhutan is wrong. Its population is still relatively young, and its elderly share is well below Sri Lanka's.
• India is wrong. It has the largest number of elderly persons in the region in absolute terms, but its elderly share is much lower because of its large young population. Percentage and absolute numbers are different questions.
• Nepal is wrong. Its fertility decline came later, so its elderly share is lower.

The core concept is the demographic transition: falling fertility and rising life expectancy raise the proportion of older people. This links to the Mains theme of population ageing, pension and healthcare pressures, and the need for elderly welfare policy in India, which is ageing fast even though its share is still moderate.

Trap: Aspirants pick India because it is the most populous country. Absolute numbers and percentages are different measures, and the question asks for the percentage.