Zimbardo's Experiment on the Effects of Dissonance Arousal on Pain

Zimbardo's experiment on the effects of dissonance arousal on pain, in which subjects received a series of intense electric shocks under different conditions, found that:

A) subjects felt less pain when they were allowed to deliver the shocks to themselves rather than receiving them from the experimenter
B) subjects felt more pain when they were allowed to deliver the shocks to themselves rather than receiving them from the experimenter
C) subjects felt less pain when they volunteered to receive the shocks
D) subjects felt less pain when they received a large reward for receiving the shocks