Question

research that examines populations of people is
epidemiological research.
experimental research.
control research.
treatment research.

Explanation:

Epidemiological research focuses on populations of people to study the distribution and determinants of health - related states or events. Experimental research involves manipulating variables, control research may refer to having a control group in an experiment, and treatment research is more about evaluating treatments. The key here is the focus on populations which is characteristic of epidemiological research.

Answer:

A. epidemiological research