The correct answer is A. 19.76%.
The population of Bihar in 1981 was 86,387,096. The population of Bihar in 1991 was 104,069,818. The growth rate of the population of Bihar during 1981-91 decade is 19.76%.
Option B is incorrect. The population of Bihar in 1981 was 86,387,096. The population of Bihar in 1991 was 104,069,818. The growth rate of the population of Bihar during 1981-91 decade is 19.76%. This is less than 21.33%.
Option C is incorrect. The population of Bihar in 1981 was 86,387,096. The population of Bihar in 1991 was 104,069,818. The growth rate of the population of Bihar during 1981-91 decade is 19.76%. This is less than 23.38%.
Option D is incorrect. The population of Bihar in 1981 was 86,387,096. The population of Bihar in 1991 was 104,069,818. The growth rate of the population of Bihar during 1981-91 decade is 19.76%. This is less than 24.06%.