The following diagrams represent the age pyramids of different populations. Comment on the status of these populations.

(N/A) Fig. $A$: It is a triangular-shaped age pyramid. In this figure,the base,i.e.,the pre-reproductive stage,is very large compared to the reproductive and post-reproductive stages. This type of age structure indicates that the population is expanding rapidly.
Fig. $B$: It is a bell-shaped pyramid. In this figure,the pre-reproductive and reproductive stages are roughly equal. This type of age structure indicates that the population is stable.
Fig. $C$: It is an 'Urn'-shaped pyramid. In this figure,the pre-reproductive and reproductive stages are smaller than the post-reproductive stage. In this population,there are more older individuals. This type of age structure indicates that the population is declining.