Although Research Does Exist on the Effectiveness of Psychotherapy, One

Although research does exist on the effectiveness of psychotherapy, one has to be careful when generalizing these findings to the real world because

A) most studies are conducted without the consent of the patients.
B) researchers do not have to meet the standards of experimental criteria when comparing therapies.
C) researchers do not know or have any control over the participants in their studies.
D) most studies are conducted in a research context.
E) most studies are conducted without the participation of the therapists.