The term population explosion means

The population of India in the early $21$st century was approximately: (in $crore$)

Statement $1$: Human population doubles after every $35 \; \text{years}$ as against $200 \; \text{years}$ in $1600-1800$.
Statement $2$: Rapid increase is due to better health facilities.

The minimum number of females per $1000$ males in India (as per the $2011$ Census) is found in which of the following union territories?

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

Population explosion is: