Which of the Following Variations of Stanley Milgram's (1963)original Obedience

Which of the following variations of Stanley Milgram's (1963) original obedience experiment provides the strongest evidence of the operation of normative conformity when participants administer electric shocks to a confederate learner?

A) When another (confederate) participant refuses to continue,participants obey less.
B) When the participants are in the same room as the learner,they obey less.
C) Older participants are less likely to obey than are younger participants.
D) Participants are less likely to obey when they believe that the learner will have a chance to "teach" them later.