Passage Summary: Scientists have a theory that fish oil is healthy. They found a study where fish-eaters had healthier hearts, so they claim this proves their fish oil theory is right.

Conclusion: A study showing that people who eat fish twice a week have lower heart disease rates supports the theory that omega-3 fatty acids provide health benefits.

Reasoning: The study found that middle-aged fish-eaters are 30 percent less likely to develop heart disease than those who do not eat fish.

Analysis: The argument relies on a causal assumption: it assumes that the heart benefits in the study were actually caused by the omega-3 fatty acids and not some other factor. For this study to truly support the specific 'omega-3' theory, we must assume that the fish-eaters weren't also doing something else—like exercising more or avoiding red meat—that actually caused the health boost. Look for an answer that the argument *needs*, such as the idea that the heart disease reduction wasn't caused by something other than the fish consumption.