According to psychoanalytic theory, people have unconscious beliefs that are kept from becoming conscious by a psychological mechanism termed "repression." Researchers investigating the nature of this mechanism observed occasions on which a patient undergoing therapy became aware of and expressed a previously unconscious belief. They found that such occasions were marked by an unusual decrease in the patient's level of anxiety.

If the information above is true, and if the researchers' investigation was properly conducted, then which of the following must also be true?

(A) Changes in the patient's anxiety level during therapy can generally be used as an accurate measure of the extent to which the patient is becoming conscious of previously repressed beliefs.

(B) Even when one of a patient's unconscious beliefs remains unconscious, researchers are sometimes able to discover this belief.

(C) If psychoanalytic theory is correct, then most conscious beliefs originate as unconscious beliefs.

(D) Researchers were able to distinguish expressed beliefs that had previously been unconscious from those that had long been conscious but that the patient had not previously expressed.

(E) Although the beliefs on which the mechanism of repression works are all unconscious, the operation of the mechanism itself is something of which patients are consciously aware.

Please answer with explanation.