In a Study of the Effectiveness of Cognitive Therapy on Anxiety

In a study of the effectiveness of cognitive therapy on anxiety, fifty anxious patients are divided into two groups. One group gets cognitive therapy, the other a fake kind of therapy that should have no benefit. However, the patients can tell that the second form of treatment is a fake. The study is weak because ____.

A) its placebo condition did not control for expectancy
B) it did not include an independent variable
C) it confuses experimental designs with correlational designs
D) it did not have a placebo condition