Passage Summary: A factory makes a chemical that causes a specific health problem, and since that health problem appeared in local wildlife after the factory opened, the factory must be leaking that chemical.

Conclusion: The river is definitely being contaminated by pesticides from the local plant.

Reasoning: The plant produces pesticides known to cause sterility in small mammals, and sterility in local otters increased right after the plant opened.

Analysis: This argument suffers from a 'correlation equals causation' flaw, specifically the error of assuming a specific cause just because a known effect is present. While the plant *could* be the culprit, the argument fails to rule out other potential causes for the increase in otter sterility, such as a different pollutant or a natural disease. In abstract terms, the logic is: X is known to cause Y; Y occurred after X appeared; therefore, X caused Y. To match this flaw, look for an answer that identifies a known cause and an observed effect, then concludes that the cause must be responsible without considering alternatives.