Passage Summary: Researchers looked at a group of people and found that the ones who worked out were less likely to die during the study, leading them to conclude that exercise makes you live longer.

Conclusion: Engaging in regular exercise has the potential to lengthen a person's life.

Reasoning: A study of same-aged individuals found that those who exercised regularly were significantly less likely to die during the observation period.

Analysis: This argument jumps from a correlation (exercise and survival) to a causal conclusion (exercise causes survival). To strengthen this, we need to address potential 'lurking variables' or the possibility of reverse causation. For instance, if the people who didn't exercise were already sick, that would explain their higher death rate better than a lack of exercise would. Look for an answer that rules out these alternative explanations or provides more evidence that the exercise itself was the active ingredient in their longevity.