The correct option is C
The assertion is true but the reason is false
A population is composed of individuals belonging to different age groups at any given time. The individuals in a population can be divided into three age groups: pre-reproductive, reproductive and post-reproductive age groups.
The graphical representation of the age composition of a specific population is called the age pyramid.
Age pyramid is obtained when the per cent individuals of a given age or age group is plotted for the population
The base of the pyramid consists of individuals of pre-reproductive age group, reproductive individuals in the middle and the post-reproductive individuals are placed at the top of the pyramid.
The shape of the age pyramid gives us an idea about the growth status of the population. It is used by demographers who study human population to predict the growth status of a population whether the population is growing, stable or declining.
The age pyramid of an expanding population has a broad base as the number of pre-reproductive individuals is higher when compared to other age groups. The reproductive individuals are moderate in number and individuals of post-reproductive age group are less. This population will certainly grow in the future.
Hence, the assertion is true but the reason is false.