Passage Summary: Certain chemicals cause hormone spikes in reptiles, which in turn lead to specific physical deformities. Since we found alligators with these deformities, the chemicals must be in the water.

Conclusion: Industrial by-products have likely contaminated the swamp's ecosystem.

Reasoning: Industrial by-products cause high hormone levels in reptiles, and high hormone levels are the only known cause of certain developmental abnormalities found in local alligators.

Analysis: The argument falls into a classic trap by assuming that because a cause (by-products) can lead to an effect (abnormalities), it must be the only cause. While the stimulus states that abnormal development occurs only with elevated hormones, it never says that industrial by-products are the only thing that can elevate those hormones. To find the flaw, look for an answer that points out the possibility of other, perhaps natural, factors causing the hormonal surge in these alligators.