Under normal conditions, ..................... are the most important factors influencing population, density.

Any species growing ...$A$... under unlimited resource conditions can reach enormous population densities in a short time. Darwin showed how even $\ldots$ $B$... growing animal like elephant could reach enormous numbers in absence of check and that characteristics of organism is called $C$

Choose the correct option for $A , B$ or $C$ respectively

If natality is represented by $-B$

If mortality is represented by $-D$

If immigration is represented by $-I$

If emigration is represented by $-E$

If population density is represented by $-N$

Then population density at time $t+1$ is represented by

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

The primary cause behind rapidly growing population of the world in recent times is