What Conclusion Can Be Drawn from Stanley Milgram's Experiments on Obedience

What conclusion can be drawn from Stanley Milgram's experiments on obedience?

A) The more distance between the controller and the controlled,the more likely people would be to engage in cruel acts.
B) Once people gave the first shock the incremental threshold was broken and so they were more likely to administer more 'lethal' shocks.
C) When Milgram introduced instructors that would disagree with each other - creating polyphony of voices - people were less likely to administer shocks.
D) all of these