The correct answer is D) Demographics.
The term "Demographics" correctly completes the center circle in the chart above.
When researchers are doing their investigations, for instance, marketing research, they have to take into consideration, Demographics. This term studies the population to be observed in terms of race, gender, age, income, education, birth, and death rates, and other socio-economic information that can help researchers in their evaluations and interpretations. Governmental agencies, corporations, research institutes, universities, and other constituencies need demographics to collect information and make decisions.