Which of the Following Is NOT True of Therapy Outcome

Which of the following is NOT true of therapy outcome research?

A) Even when a therapy works, researchers often cannot know exactly what it is about the therapy that works.
B) Some researchers believe it is unethical to withhold treatment or to provide a treatment they believe is ineffective for people in distress.
C) Therapists who vary the dosage of a drug or deviate from a study's procedure for psychological intervention may compromise the results of the study.
D) In the real world, mental health services are delivered in controlled, high-quality atmospheres, and patients fit neatly into the criteria for an "optimal patient."