A small town relies heavily on its fishing industry. Recently, a new factory opened upstream, and shortly thereafter, the fish population in the town's river significantly declined. Local environmentalists conclude that the factory's operations are directly responsible for the decline in fish. Which of the following, if true, would most seriously weaken the environmentalists' conclusion?
- AThe factory primarily produces non-toxic plastic components, which are inert in water.
- BStudies show that fish populations naturally fluctuate due to seasonal breeding patterns and migration.
- CThe factory implemented advanced wastewater treatment systems that exceed environmental regulatory standards.
- DA severe drought began shortly after the factory opened, significantly lowering the river's water levels.
Show answer & explanationAnswer & explanation
Correct answer: D. A severe drought began shortly after the factory opened, significantly lowering the river's water levels.
The environmentalists conclude the factory is *directly responsible* for the fish decline, based on a 'post hoc ergo propter hoc' fallacy (after this, therefore because of this). Option B introduces a strong alternative cause (a severe drought and lowered water levels) that occurred concurrently with the factory's opening, providing a more plausible explanation for the fish decline and weakening the direct causal link to the factory.
Why the other options are wrong
- A. The non-toxic nature of the products makes it less likely that the *products* themselves are causing harm, but doesn't rule out other factory operations (e.g., heat discharge, noise) as a cause, making it weaker than a direct alternative cause.
- B. While natural fluctuations exist, a 'significant decline' usually implies something beyond normal. This option is less direct than a specific, impactful event like a drought.
- C. This suggests the factory is environmentally responsible, directly weakening the claim that its operations caused the decline by implying it's not polluting.
Alternative Cause (Weakening)
Presenting a different, plausible explanation for an observed phenomenon that competes with the proposed cause, thereby weakening the original causal claim.
- Introduces a confounding variable.
- Challenges the uniqueness of the proposed cause.
- Often involves a concurrent event or pre-existing condition.
Memory trick: Just because A happened before B, doesn't mean A caused B.