Which option correctly relates population change and age structure?

Correct answer: Births, deaths and migration can change the shares of different age groups.

Answer: A. Age structure means the proportion of children, working-age adults and older people in a population. Population processes do not affect all age groups in exactly the same way. Births add mainly to the youngest group, deaths may affect age groups differently, and migration is often concentrated among particular ages, especially young adults, though this is not identical everywhere. Therefore these processes can change the shares of age groups. A is correct. B is incorrect because age structure is an important population characteristic. C is incorrect because migration changes the number and composition of people, not only soil. D is incorrect because births add people; they do not automatically increase the geographical area of a place. Age structure helps planners estimate future needs for schools, jobs and health care. Memory cue: age structure asks “how many are young, working-age and old?”