Correct Answer: (a) Migration
Note: Push and pull factors are commonly associated with the study of human migration. In this context, push factors are those that drive people to leave their cur- rent location, such as economic hardship, political in- stability, environmental disasters, or social conflict. Pull factors are those that attract people to a particular destination, such as better economic opportunities, political stability, or a more favorable environment. Both push and pull factors are relevant to any population that experiences migration or movement, whether it be internal or international migration.