In a study designed to test the effects of a new drug developed to treat Alzheimer's disease,half the patients were given the actual drug while the other half of the patients were given a placebo (sugar pill) .In this study,which group is the control group

A)  the group that showed no evidence of an improvement in their memory 
B)  the group that received the actual drug 
C)  the group that received the placebo 
D)  no control group in this study

The control group in this study is the group that received the placebo. The control group is used to compare the results of the experimental group (those who received the actual drug) to determine if the drug had a significant effect. The group that showed no evidence of improvement in their memory is not necessarily the control group, as it could be either the experimental group or the placebo group. Option D is incorrect, as all studies require a control group to ensure accurate results.