Which of the Following Statements About Voluntary Participation in Research

Which of the following statements about voluntary participation in research is FALSE?

A) Offering large rewards for participation in research can be coercive if the reward is perceived to be "too good to refuse."
B) It is acceptable for people in positions of power, such as employers, to require their subordinates to participate in research.
C) If instructors "strongly encourage" students to participate in research, the students may conclude that they are required to participate.
D) Only monetary inducements to participate in research raise issues of voluntary participation, not in-kind services such as psychotherapy.