You plan a trial testing a new flavored nutritional beverage. To choose the best control, which is most appropriate?

• A. Assign control participants to an unrelated exercise program so they feel engaged while the treatment arm receives the beverage, avoiding the need for blinding
• B. No control at all; give everyone the new beverage and compare outcomes to historical norms from other studies, which avoids participant inconvenience
• C. A visually and taste-matched placebo beverage without the active ingredient, with participants randomized to beverage A or placebo to isolate the active ingredient’s effect
• D. Use a control beverage that differs in both taste and appearance to make it obvious who is getting the active product, because transparency increases compliance

Answer: (C)