One of Kurt Lewin's Boldest Intellectual Contributions to Social Psychology

One of Kurt Lewin's boldest intellectual contributions to social psychology was

A) promoting the use of observational methods.
B) applying behavioural principles to the topic of social influence.
C) applying Gestalt principles to social perception.
D) investigating the impact of culture on behaviour.
E) reminding social psychologists that objective physical attributes of a social stimulus are important.