What Do the Studies by Milgram on Shock-Giving), Hofling Et

What do the studies by Milgram on shock-giving) , Hofling et al. on the nurse-physician relationship) , Bickman on the power of a uniform) , and Doob and Gross on horn-honking at a traffic light) have in common? They all:

A) demonstrate the effect of authority influence on human behavior.
B) show that males and females react differently to authority influence.
C) show that people typically underestimate the strength of authority on behavior.
D) all of the above.
E) only a and c.