Correct Answer: (b) 1961-1971
Solution:The highest percentage change in the population of India was observed in the Census year 1971 (in 1961-71 decade). The decadal growth rate during this period was 24.80 per- cent. Whereas in the Census year 1981, it was 24.66%, in 1991, it was 23.87% and it was 21.54% in the Census year 2001. As per Census 2011, the decadal growth rate is 17.7 percent.