PrepTest 124, Section 3, Question 4
A recent test of an electric insect control(39 more words not shown)
Which one of the following,(7 more words not shown)
- AA careful search(13 more words not shown)
- BA very large(13 more words not shown)
- CThe device is(13 more words not shown)
- DMany of the(10 more words not shown)
- EThe device does(11 more words not shown)
Reading the argument
What if there were only twelve mosquitoes to kill?
Twelve is a small part of the more than 300 dead insects. But the question is whether the device controls mosquitoes, not whether mosquitoes make up most of its victims. If only twelve mosquitoes were nearby and the device killed all twelve, that small share of the total would hide a very effective result.
We haven't been told how many mosquitoes were there in the first place. Maybe this location simply had many more beetles or other insects. The total number of dead insects doesn't give us the missing mosquito count.
What we’re looking for
We're weakening the claim that the device won't significantly help control mosquitoes. My prediction is evidence that those twelve deaths represented most or all of the local mosquitoes. We don't need the device to ignore every other insect in order to work against mosquitoes.
Working the answers
- ACorrect
After the test, a careful search found no living mosquitoes nearby. That supports the possibility we identified: the device may have killed the available mosquitoes, despite their small share of all the insects killed. A search finding none doesn't prove the device killed every mosquito that was ever there, but it gives us a concrete reason to doubt the claim that the device failed to control the local population.
- B
Many of the insects attracted could be other kinds even if the device attracted and killed every mosquito nearby. We still need the number or proportion of mosquitoes left alive. The mix of insects attracted doesn't by itself establish that mosquitoes escaped control.
- C
Whether the device does more harm than good overall is a different question. It could kill many beneficial insects and still be effective at killing mosquitoes. This comparison doesn't give us a reason to reject the specific claim about mosquito control.
- D
Killing insects that eat mosquitoes could remove a natural check on the mosquito population. That gives us another reason to doubt the device's usefulness against mosquitoes, which supports the author's concern rather than weakening it. These other insects matter because their loss could help mosquitoes survive.
- E
It needn't kill every insect it attracts to have a significant effect. A device that killed 90 percent of nearby mosquitoes, for example, could help control them without killing all of them. E doesn't tell us which insects survive or how many mosquitoes remain. It supplies no evidence of the successful control we need to weaken the conclusion.
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