The term population explosion means

$Statement \; 1$: Zero population growth should be achieved as early as possible to control human population.
$Statement \; 2$: This requires not two children per couple but a little more effort on reduction of this number.

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

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

$Statement 1$: Over-population has become a serious problem in the developing countries.
$Statement 2$: It does not exhaust natural resources, causes unemployment and pollution.