In a controlled experiment where one group receives the drug dissolved in water and a second group receives water alone, the second group serves as a

• A. Group A
• B. Group B
• C. Both groups
• D. Control group

Answer: (D)

The key idea here is using a baseline to isolate the effect of a treatment. In this setup, the group that receives only water serves as a control because they experience everything except the active drug. This makes them a baseline for comparison, so any differences observed between the two groups can be attributed to the drug itself rather than to placebo effects, random variation, or other factors. By comparing outcomes from the drug group to this control group, researchers can determine whether the drug truly has an effect.