Which of the following is a cause of population explosion in India?

The correct answer is Option (4) → All of these.

In India, better health facilities and living conditions brought down deaths, especially of mothers and infants. With fewer deaths and more people in the reproducible age, the population grew very fast. NCERT names a rapid decline in death rate, maternal mortality rate (MMR) and infant mortality rate (IMR) as probable reasons.

Option (1) Decline in MMR. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. A decline in MMR (maternal mortality rate) means fewer mothers die in childbirth.

Option (2) Decreased IMR. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. Decreased IMR (infant mortality rate) means more infants survive.

Option (3) Better health care. — Correct statement, but it is only one of the correct points, so on its own it is not the answer. Increased health facilities with better living conditions had an explosive impact on population growth.

NCERT Extract:
Population Stabilisation and Birth Control – “In the last century an all-round development in various fields significantly improved the quality of life of the people. However, increased health facilities along with better living conditions had an explosive impact on the growth of population. … A rapid decline in death rate, maternal mortality rate (MMR) and infant mortality rate (IMR) as well as an increase in number of people in reproducible age are probable reasons for this.”