Researchers wanted to evaluate whether a certain herb improved memory in elderly adults as measured by objective tests. To do? this, they recruited 88 men and 131 women older than 55 years and in good health. Participants were randomly assigned to receive the? herb,30 mg 3 times a? day, or a matching placebo. A measure of memory improvement was determined by a standardized test of learning and memory. After 6 weeks of? treatment, the data indicated that the herb did not increase performance on standard tests of? learning, memory,? attention, and concentration. These data suggest? that, when taken following the? manufacturer's instructions, the herb provides no measurable increase in memory or related cognitive function to adults older than 55years with healthy cognitive function. Complete parts? (a) through? (g) below.

?(f) What is the control group in this? study?

A. The placebo group serves as the control group because this group corresponds to the reference point that will be compared to the other group.

B. The men serve as the control group because this group corresponds to the herb that is being tested.

C. The women serve as the control group because this group corresponds to the herb that is being tested.

D. The herb group serves as the control group because this group corresponds to the reference point that will be compared to the other group.