PT156 S4 Q12 ExplanationEcologist: El Niño, a global weather

Answer choices, explained

1. A

   Irrelevant1% picked this

   In region T, there is typically much less rainfall in summer than there

   This choice compares rain patterns between seasons in region T, but it doesn’t affect the prediction about future rodent populations. If there's more rain in winter, then we'd predict rodent populations to surge in winter, but this doesn't have anything to do with whether those surges will be bigger/smaller/same in coming decades.

   1%
2. B

   Opposite (if anything)3% picked this

   Rodent populations in region T often diminish during long periods in which there are

   This "less rain, less rodents" type of answer seems to corroborate the argument's correlation between rodents and heavy rain. So if anything it would strengthen.

   3%
3. C

   Unclear Impact15% picked this

   In many regions that, on average, experience substantially more winter rainfall than region T does, average rodent populations are considerably lower than

   This seems somewhat promising, because it sounds like it's decoupling the argument's link between heavy rain and higher rodent populations. But since we're comparing different regions, we don't know what other factors might be contributing to there being lower rodent populations in regions with more rain. If rain is good for rodents, but snakes are bad for rodents, a region with lots of rain and lots of snakes could potentially have fewer rodents than a region with less rain but no snakes. To undermine the rain/rodent link, we'd want to hear "within a given region, the rodent populations were lower when there was lots of rain than when there was much less rain".

   15%
4. D

   Correct72% picked this

   In region T, winters marked by relatively high rainfall have usually not been marked by long

   Why this is right

   We know that El Nino causes heavy winter rainfall, but the trigger the Evidence provides for a boost in rodent population is a long period of sustained rain (like it rains for 5 days straight), not just heavy winter rain. This answer shows how coming decades could have heavier winter rainfall but not actually have any uptick in long periods of sustained rain. This provides disconnect in the causal chain the author was selling us.

   Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.

   72%
5. E

   Unclear Impact9% picked this

   The global warming caused by air pollution produces a number of effects, other than the increase in the frequency of El Niño,

   While stating that global warming could have other effects on rodent populations, it doesn’t specify whether these effects would increase or decrease rodent numbers. Consequently, it creates uncertainty but doesn’t directly weaken the argument since the net effect is unclear.

   9%