PrepTest 94+, Section 4, Question 12
Ecologist: El Niño, a global weather phenomenon that occurs once every several years, is expected to become more frequent in coming decades due to the global warming caused by air pollution. In region T, El Niño causes heavy winter rainfall. Since rodent populations typically increase during long periods of sustained rain, it is likely that average rodent populations in region T will also increase in coming decades.
Ecologist: El Niño, a global weather phenomenon that occurs once every several years, is expected to become more frequent in coming decades due to the global warming caused by air pollution. In region T, El Niño causes heavy winter rainfall. Since rodent populations typically increase during long periods of sustained rain, it is likely that average rodent populations in region T will also increase in coming decades.
Ecologist: El Niño, a global weather phenomenon that occurs once every several years, is expected to become more frequent in coming decades due to the global warming caused by air pollution. In region T, El Niño causes heavy winter rainfall. Since rodent populations typically increase during long periods of sustained rain, it is likely that average rodent populations in region T will also increase in coming decades.
Ecologist: El Niño, a global weather phenomenon that occurs once every several years, is expected to become more frequent in coming decades due to the global warming caused by air pollution. In region T, El Niño causes heavy winter rainfall. Since rodent populations typically increase during long periods of sustained rain, it is likely that average rodent populations in region T will also increase in coming decades.
Which one of the following, if true, would most weaken the ecologist's argument?
In region T, there is typically much less rainfall in summer than there is in winter.
Rodent populations in region T often diminish during long periods in which there are no heavy rains.
In many regions that, on average, experience substantially more winter rainfall than region T does, average rodent populations are considerably lower than they are in region T.
In region T, winters marked by relatively high rainfall have usually not been marked by long periods of sustained rain.
The global warming caused by air pollution produces a number of effects, other than the increase in the frequency of El Niño, that could affect rodent populations.
Explanations
The passage tells us a few things.
First, El Niño is expected to become more frequent thanks to global warming. Second, El Niño causes heavy winter rainfall in region T. Third, rodent populations typically increase during long periods of sustained rain. Got it.
Then, the passage concludes that it's likely average rodent populations in region T will increase in coming decades. Not so fast. That's possible, but by no means proven.
We're asked to weaken the argument. I can think of a few objections.
For example, what if heavy winter rains cause mass breeding of rodent-killing predators? That would keep the rodents under control. Or, what if global warming—the thing increasing El Niño's frequency—will adversely affect rodents? Or what if heavy winter rain in region T happens in intense, intermittent bursts instead of sustained monsoons? Any of these ideas would weaken the argument.
Let's take a look.
Nope, irrelevant to the argument. How does less summer rainfall tell me anything about rodent populations relative to El Niño, which affects region T in the winter?
No. Cool story bro, but we're supposedly about to deal with long periods of heavy rains (even if not sustained).
No. Again, cool story, but I'm concerned with region T, not other regions.
Bingo. This is the answer. If heavy winter rain in region T ≠ sustained period of rain, then the conditions that lead to increased rodent population may not occur, even in light of more frequent El Niño events.
Nope. Such a trap. So global warming could affect the rodents? Great, but I need it to affect the rodents. Could disqualifies this answer.
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