Human geography primarily studies:

Human geography primarily focuses on the relationship between people and their environments, analyzing how human activities influence and modify the physical landscape. This branch of geography examines various aspects including urban development, population distribution, cultural landscapes, and economic and political practices. The emphasis is on the interactions between societies and their environments, understanding how societal factors shape geographical spaces and vice versa.

The study encompasses various topics such as migration patterns, land use, and the spatial distribution of resources, all emphasizing the impact people have on the physical world. This is why this choice accurately reflects the primary focus of human geography. Other options pertain to different aspects of geography or history; for instance, the effects of natural disasters are more aligned with environmental geography, and the distribution of animal populations pertains to the field of biogeography rather than human geography. Additionally, the history of human civilizations relates more to historical geography rather than human geography's focus on contemporary human-environment interactions.