For question 14, my reasoning was that choice A, if true, provides a different explanation to why the traps have been less effective than what the scientists have hypothesized. Whereas the scientists attributed the decrease to a resistance to the pesticide, choice A attributes it to the pests having an increased aversion to to eating the glucose that is mixed in with the pesticide. Is this reasoning correct?
Can you also explain the reasoning behind #19 and #24?
Thanks!
#19.
This one's all about the numbers. Any time you work a % argument, be on the lookout for improperly drawn conclusions regarding the actual numbers.
Here, the author concludes that the NUMBER of knee injuries has not decreased. This conclusion is based on the fact that the PERCENTAGE of knee injuries has increased. This is a % of all injuries.
A quick scan of the choices, looking for mention of percentages or numbers, eliminates all but C and D.
The author does not ignore (C). It wouldn't affect the argument one way or another if the # of skiers had increased or decreased. The conclusion is not about the % of skiers that get injured, but rather the % of injuries that are knee injuries.
(D) addresses this. "Increase in proportion" = the increase in %. Yes, the author assumes that this correlation rules out an overall decrease in the # of knee injuries, because the conclusion is that that # has increased.
It's possible that the NUMBER of total injuries, and of knee injuries, is way, way down. For example, the case may be that 20 years ago there were 15,000 injuries a year and 11% of them were knee injuries. Now, there are 160 injuries a year and 16% of them are knee injuries. Clearly, the actual NUMBER of knee injuries need not have increased.