For Harry Stack Sullivan, It Is Most Important to Examine

For Harry Stack Sullivan, it is most important to examine

A) what people do when they are alone and unobserved.
B) how people feel when they have been rejected by others.
C) what people do when they are alone but know they are being observed.
D) how extroverts differ physiologically from introverts.
E) how people differ physiologically when they are alone versus with others.