Answer:
The group in the program of aerobic exercise.
Step-by-step explanation:
Researchers Lisa McCann and David Holmes performed a study with a group of undergraduate females, all with mild depression; as it states in the question, the study consisted of a control group; a group that was asigned to a placebo treatment, that were relaxation exercises; and a group that participated in aerobic exercise.
Findings of the study indicated that women in all three groups reported that their depression had reduced after the ten week treatment, however, findings also indicated that females participating in aerobic exercise reported the greatest decrease in depression. Along with McCann and Holmes' study, there is other existing research that has reported findings that are consistent with the results of their study: exercise helps reduce depression and anxiety.