Which of the Following Did Masters and Johnson NOT Use

Which of the following did Masters and Johnson NOT use to maintain ethical standards in their laboratory studies of sexuality?

A) pre-screening interviews to remove distressed individuals
B) informed consent,ensuring the participants knew their right to leave the study at any point
C) those participants who engaged in intercourse remained anonymous from their partners through the use of false names
D) follow-up contact was made with participants to ensure they suffered no ill effects from their participation in the study