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

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

A)  Most individuals show the best progress when they are treated by a therapist trained in multiple approaches. 
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 clinical psychologist. 
D)  There is no reliable connection between therapists' professional background and therapeutic efficacy.