According to the Text, Why It Is Difficult for Psychologists

According to the text, why it is difficult for psychologists to scientifically test for Freud's theory of unconscious suppression?

A) Participants may not be willing to report embarrassing thoughts with researchers.
B) Experiments involving anxiety-inducing thoughts are often prohibited by ethics review boards.
C) Most psychologists do not believe Freud's theory of the unconscious to be correct.
D) There are currently no methods available for testing the unconscious.