In Terms of the Relationship Between Therapists' Professional Background and Therapeutic

In terms of the relationship between therapists' professional background and therapeutic efficacy,researchers have found that

A) most individuals show the best progress when they are treated by a clinical psychologist.
B) most individuals show the best progress when they are treated by a certified psychiatrist.
C) most individuals show the best progress when they are treated by a therapist trained in multiple approaches.
D) for certain types of problems, some approaches to therapy are more effective than others.