How Does the Gender of the Therapist Influence the Effectiveness

How does the gender of the therapist influence the effectiveness of psychotherapy?

A) Generally speaking,male clients experience more effective therapy with male therapists.
B) The gender of the therapist does not influence effectiveness for male or female clients.
C) Usually,female therapists are more effective in treating men than male therapists.
D) Female therapists do a significantly more effective job at treating female clients.