The population growth of India from $1981$ to $1991$ is (in $\%$)

Birth rate is directly proportional to

In India,the number of females per $1,000$ males had been constantly decreasing. In which of the following years did this number increase?

Human population in India reached the $1$ billion mark by the year . . . . . . .

July $11$ is observed as ........

Presently, the world population doubles after every (in $years$)