The correct answer is (a) 1951-1961.
The decadal growth of population in India was highest during 1951-1961, with a growth rate of 21.5%. This was due to a number of factors, including a decline in mortality rates, an increase in fertility rates, and a decrease in the age at marriage.
The decline in mortality rates was due to a number of factors, including improvements in public health, such as the introduction of vaccination programs, and the expansion of healthcare services. The increase in fertility rates was due to a number of factors, including a decline in the cost of raising children, an increase in the status of women, and a change in the traditional role of women. The decrease in the age at marriage was due to a number of factors, including an increase in the level of education, an increase in the number of women in the workforce, and a change in the social norms surrounding marriage.
The high growth rate of population during 1951-1961 had a number of consequences, including an increase in the demand for food, housing, and other resources, and an increase in environmental pollution. The government of India took a number of measures to address the challenges posed by the high growth rate of population, including family planning programs, the promotion of education and employment for women, and the provision of basic amenities such as water and sanitation.
The decadal growth of population in India has declined since 1951-1961. This is due to a number of factors, including a decline in fertility rates, an increase in the age at marriage, and an increase in the level of education. The government of India has continued to take measures to address the challenges posed by the high growth rate of population, and the population growth rate is expected to continue to decline in the future.