PrepTest 118, Section 1, Question 12
Biologists have noted reproductive abnormalities in fish that(55 more words not shown)
Which one of the following(8 more words not shown)
- ASome of the(14 more words not shown)
- BThe rate at(13 more words not shown)
- CNormal river currents(13 more words not shown)
- DSome of the(18 more words not shown)
- EThe connection between(9 more words not shown)
Reading the argument
The fish live just downstream of paper mills, and the mills release something that can change their hormone concentrations. That sounds like a possible explanation for the reproductive problems. It isn't proof, but it's worth investigating.
The author tries to rule dioxin out. During a shutdown, the fish's hormone levels return to normal quickly, even though dioxin breaks down slowly. The reasoning seems to be that dioxin should still be affecting the fish if it were the cause. If the fish recover while the proposed cause remains, perhaps we should blame something else.
I'm not ready to dismiss dioxin. What if the hormones return to normal after the chemical has already done lasting damage? Normal hormone levels wouldn't necessarily mean the reproductive system has recovered. That is my initial concern, although it doesn't yet explain exactly what happens to the dioxin during a shutdown.
What we’re looking for
We need to weaken the case against dioxin. I'd look for a reason that the quick recovery doesn't justify ruling it out. The answer might develop the lasting-damage concern, or it might expose another problem with the author's account.
Working the answers
- A
The funding gives paper manufacturers an interest in the result, but it doesn't show that the research is inaccurate. A manufacturer could fund a study that correctly reports the fish's hormone levels. We need a problem with the causal reasoning or the evidence, not an assumption that an interested sponsor guarantees bad research.
- B
Which conditions make dioxin break down faster, and do those conditions occur here? B doesn't say. Decomposition could vary while remaining slow in this river. The general existence of variation doesn't establish that the author's observation is wrong or explain the quick recovery.
- CCorrect
This takes a different route from the lasting-damage idea. Dioxin doesn't have to break down to stop exposing these fish; it can move away from them.
When the mill operates, it keeps adding dioxin, so more of it passes the fish just downstream. When the mill shuts down, that input stops, and the river can carry the dioxin already present far downstream within hours. The chemical may persist in the environment without remaining beside this fish population.
That makes quick recovery compatible with dioxin being the cause. The author treated slow decomposition as a reason to expect continued exposure, overlooking the current's ability to remove the chemical from this location.
- D
This resembles the initial concern: some bodily changes can last after hormone levels recover. But it doesn't identify dioxin as their cause or explain why hormone concentrations recover quickly despite the chemical's slow decomposition. Those lingering effects could come from a different substance. C directly explains how the recovery can occur when dioxin was responsible.
- E
We don't need a complete understanding of the hormone-reproduction connection to assess the author's specific inference. E doesn't explain why dioxin could still be responsible despite the quick recovery. General uncertainty about the mechanism leaves the key shutdown evidence unaddressed.
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