According to the Authors of Your Text, What Is the Most

According to the authors of your text, what is the most plausible explanation as to why the U.S.soldiers followed their lieutenant's orders to massacre the citizens of the peaceful village of My Lai during the Vietnam War?

A) They were conforming in a confusing situation.
B) They were bloodthirsty assassins.
C) Soldiers tend to be more aggressive than the average person.
D) They were expressing implicit prejudice.