The correct answer is (a) 1971.
The population of India increased from 548.1 million in 1971 to 683.3 million in 1981, a growth rate of 24.65%. This was the highest percentage change in population recorded in any census year in India.
The population of India continued to grow at a rapid pace in the following decades, reaching 1.21 billion in 2011 and 1.38 billion in 2021. However, the growth rate has slowed down significantly, from 24.65% in 1971-1981 to 17.64% in 2001-2011 and 12.8% in 2011-2021. This is due to a number of factors, including a decline in fertility rates, an increase in life expectancy, and an increase in urbanization.
The rapid growth of the Indian population has had a significant impact on the country’s economy, environment, and society. The government has implemented a number of policies to address the challenges posed by population growth, including family planning programs, education initiatives, and infrastructure development.