Passage Summary: A study found that people taking a cholesterol-lowering drug had fewer heart attacks. Since heart patients usually have high cholesterol, the researchers concluded that the lower cholesterol itself was the reason for the health improvement.

Conclusion: Reducing cholesterol levels is the cause of the decreased risk of heart disease.

Reasoning: A drug that lowers cholesterol also lowered heart attack rates, and people with heart disease typically have high cholesterol.

Analysis: This argument suffers from a classic correlation-versus-causation flaw. While the drug pravastatin lowers cholesterol and reduces heart attacks, the author assumes the former causes the latter. However, the drug might have other effects—perhaps it reduces inflammation or strengthens artery walls—that are actually responsible for the benefits. Look for an answer that identifies this failure to consider that the drug's other effects, rather than the cholesterol reduction itself, might be the true cause of the improved health outcomes.