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

The $20^{th}$ century has witnessed a remarkable increase in the population of the world and especially in India. One major factor for this is that

In India,if the marriage age is changed to $21$ years,then:

How many persons are added to the Indian population per year?

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

In India,the population crossed the one billion mark in May $2000$. The probable reasons for this are a decline in:
$A.$ Maternal mortality rate $(MMR)$
$B.$ Infant mortality rate $(IMR)$
$C.$ Number of people in the reproductive age group
$D.$ Death rate