The correct option is B 1911-1921
Population of India in 1911 was 252.09 million and it dropped to 251.32 million in 1921, registering a decline of -0.31%. For this reason, 1921 has been termed by the Census Commissioner as the year of Great Divide. Growth has been positive for all other decades, it was moderate from 1921-1951 and then quickened post 1951.