Answer:
A) The age classes, in 5-year ranges
Explanation:
The number between the bars are the age classes, and the bars represent the populartion, in millions, belonging to the corresponding age class.
A population pyramid like the one attached below usually does not show the number of people born in a particular year. However, this information can be estimated by looking at the year the population pyramid was elaborated, and substracting from that year the corresponding ages illustrated in the pyramid.
