The following is a definition of what? the study of variations and changes in the distribution, makeup, movement, and environmental relationships of a population

a. population geography

b. demography

c. population pyramid

d. cartography

The answer would be : B. Demography

Basically, The main purpose of demography is to require mass Data, such us an effect of Bill A to the people, or average age for drug addiction, etc

The result data that acquired by Demographic Study, will be further used by institutions (could be a corporation, non profit or Governmental institution) to make their decision