Phenomenal and rapid increase of population in a short period is called

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

The best solution to the population problem in India is to

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

Explain the requirement for the control of population growth and birth control.

The total population of the world by the end of the $20^{th}$ century reached approximately: