Various age pyramids (P-R) for human population are shown below. Select the option with correct identification.

	Expanding type	Declining type
1.	P	Q
2.	P	R
3.	Q	R
4.	Q	R

Triangular: It is a graphic representation of a young or growing population which appears like a triangle. The population has a very high proportion of pre-reproductive individuals, proportionate numbers of reproductive individuals is moderate and post reproductive individuals are proportionately fewer. Because of the very large number of pre reproductive individuals, more and more of them enter the reproductive phase and rapidly increases the size of population.

Bell-shaped: The pyramid is bell-like with pre-reproductive individuals being only marginally more than the reproductive individuals. Population is said to be mature or stable as there is no increase or decrease in its size due to growth rate being almost zero.

Urn-shaped: It has small number of pre-reproductive individuals followed by a large number of reproductive individuals. As there are fewer individuals in pre-reproductive group, the population size will decline with time. Such a population shows a declined growth (negative growth).