When evaluating the efficacy of a new drug, which is a critical component?

Correct answer: A. Placebo (control)

• A. Correct (keyed). A placebo control is essential to demonstrate that effects are due to the drug, not expectation.
• B. Double-blinding is also critical and a defensible answer (reduces bias); the keyed answer is the placebo control.
• C. Random sampling addresses generalizability, not the efficacy comparison itself.
• D. A cross-sectional design cannot establish drug efficacy (no intervention/follow-up).

Note: Double-blinding (B) is an arguable alternative; both placebo control and blinding strengthen an efficacy trial. Keyed answer is placebo.