Passage Summary: Two lakes were losing fish; one banned fishing and got better, while the other didn't and got worse, so the ban must have worked.

Conclusion: The fishing moratorium is the likely cause of the fish population's recovery in Quapaw Lake.

Reasoning: Quapaw had a ban and recovered, while Highwater had no ban and continued to decline over the same ten-year period.

Analysis: This is a classic correlation-versus-causation setup involving a control group. To weaken the conclusion, we need to find a significant difference between the two lakes other than the fishing ban. Perhaps Quapaw had a pollution cleanup or a different water source that Highwater lacked. Look for an answer that introduces an alternative cause for Quapaw's success or Highwater's failure.