What Must a Plaintiff Prove to Show a Per Se

What must a plaintiff prove to show a per se violation of the Sherman Act?

A) That trust activity is likely to dilute efficiency among the competition.
B) That the prohibited conduct occurred.
C) That there is an unambiguous presumption of unfair trust activity.
D) An amount of economic harm meeting standards set by the Sherman Act itself.
E) That the prohibited conduct occurred and the proper amount of economic harm.