Birth rate is directly proportional to

The socio-religious cause of population growth is:

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

Which of the following is the most convincing reason for increased population growth in a country?

$A$: Population of India crossed one billion in May $2000$.
$R$: It is the result of a rapid decline in death rate,maternal mortality rate $(MMR)$,and infant mortality rate $(IMR)$,as well as an increase in the number of people in the reproductive age.

Which of the following can be taken as characteristic demographic features of the developing countries?
$(a)$ High fertility rate
$(b)$ Rapidly rising mortality rate
$(c)$ Very young age distribution
$(d)$ Rapid population growth
$(e)$ Rapidly falling mortality rate
$(f)$ Very old age distribution