Why Is Much of the Research with the Group Processes

Why is much of the research with the group processes and structures face of sociological social psychology experimental in design?

A) Collaboration between GPS researchers and biologists who favor experiments is common.
B) GPS research does not address structural issues.
C) How structured settings (e.g. the lab) influence people's perceptions and behaviors is the key research question of interest to social psychologists working in the GPS orientation.
D) Many of the independent variables of interest to GPS researchers are under their control and can be manipulated.
E) Most social psychologists who work within the group processes and structures orientation have a background in psychological social psychology.