Passage Summary: Research indicates a surprising trend where tiny rats have much higher rates of heart disease, whereas big rats are significantly healthier in that regard than average rats.

Reasoning: A study showed that small rats are twice as likely to have heart problems, while large rats are half as likely to have them, compared to average-sized rats.

Analysis: This is a Paradox question with an 'Except' twist, meaning four of the answers will provide a plausible reason for this size-to-health correlation. We are looking for the one answer that is either irrelevant or perhaps even makes the heart disease gap harder to explain. The core conflict is that we might expect larger organisms to have more heart strain, but here the opposite is true. Focus on finding the outlier that doesn't help us understand why being small is a cardiac liability or why being large is a benefit.