All the Following Statements Are Ethical Concerns About Milgram's Research

All the following statements are ethical concerns about Milgram's research EXCEPT which one?

A) Participants were not aware that they were part of a psychological study.
B) Many of the participants learned that they were potentially capable of doing harm to another person simply because they were told to do so.
C) It was stressful for participants to be in a situation where they were being ordered to do harm to another person.
D) Participants could have damage done to their self-image.