One Strategy to Evaluate the Effectiveness of Psychotherapy Is to Compare

One strategy to evaluate the effectiveness of psychotherapy is to compare people who enter psychotherapy with a control group of people who do not receive psychotherapy.When researchers combine and summarize the results of studies using this strategy,what overall conclusions emerge?

A) People in the psychotherapy group improve at about the same rate as the people in the untreated group.
B) People in the psychotherapy group actually improve at a slower rate than the people in the untreated group.
C) The people in the untreated group do not get better,while about one-third of the people in the psychotherapy group get better,about one-third deteriorate,and about one-third remain unchanged.
D) Psychotherapy is significantly more effective than no treatment in producing an improvement in symptoms.