LSAT 118 | Section 1 | Logical Reasoning: Q12

LR Question 12 Explanation

QUESTION TEXT: Biologists have noted reproductive abnormalities in fish …

QUESTION TYPE: Weaken

CONCLUSION: Dioxin is probably not the cause of the abnormalities.

REASONING: Fish recover normal hormone concentrations quickly during mill shutdowns, and dioxin decomposes very slowly.

ANALYSIS: The author’s logic is:

• Dioxin sticks around for a long time.
• The fish recover quickly.
• Therefore dioxin probably isn’t causing the problem.

But just because dioxin decomposes slowly, does that also mean it must remain near these fish during shutdowns? Not necessarily.

Something can persist in the environment for a long time while still being moved away from a particular location very quickly.

So the best weakener will explain how fish could recover rapidly even if dioxin is the culprit.

If dioxin gets swept downstream shortly after the mill shuts down, then:

• the fish near the mill stop being exposed,
• their hormone levels return to normal,
• and dioxin can still be the cause.

___________

1. This suggests possible bias in some studies, but it does not show the studies are inaccurate.
2. So decomposition rates vary. That doesn’t tell us whether dioxin decomposes quickly enough in this situation to explain the rapid recovery.
3. CORRECT. This weakens the argument, which treats slow decomposition = continued exposure. But if river currents carry dioxin far downstream within hours, then fish near the mill can recover quickly even though the dioxin itself remains intact. So the observed recovery no longer provides a reason to rule out dioxin.
4. This talks about lingering physiological effects after hormone levels change. But the argument is focused on why hormone levels recover quickly.
5. Even if the link between hormone changes and abnormalities is poorly understood, it does not undermine the specific reasoning used to rule out dioxin.