求助PREP破解中CR的难度

coffeeid

这两天做了PREP破解的CR,觉得蛮难的，正确率很低。之前做GWD的CR正确率有80％＋，不知道出了什么问题，是不是两者思路有不同啊

有两道题比较困惑，版子里也没看到讨论，晒一下并请教

22.   (28829-!-item-!-188;#058&003748)

 

In the late 1980s, the population of sea otters in the North Pacific began to decline.  There are two plausible explanations for the decline:  predation, possibly by killer whales, or disease.  Of these two, disease is the more likely, since a concurrent sharp decline in populations of seals and sea lions is believed to have been caused by disease, and diseases that infect these creatures are likely to be able to infect sea otters also.

 

Which of the following, if true, most seriously weakens the reasoning?

 

(A) Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.

(B) There is no indication that the sea otter population at any North Pacific location declined in the 1980s because of substantial numbers of sea otters migrating to other locations.

(C) Along the Pacific coast of North America in the 1980s, sea otters were absent from many locations where they had been relatively common in former times.

(D) Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters' main food source.

(E) The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.

答案是A，前半句没什么疑问，但是后半句中说when this food source is scarce, seek out other prey又没有说就是sea otters ,怎么能削弱呢

33.   (31934-!-item-!-188;#058&005658)

 

When a caterpillar emerges from the egg on a tree branch, it immediately climbs upward until it finds a leaf bud to eat.  Biologists thought that this behavior displayed an innate tendency to move in the direction opposite to the pull of gravity.  In a recent experiment, a strong light source was placed at the bottom of a tree, and caterpillars, after hatching, climbed downward.

 

Which of the following hypotheses is best supported by the statements given?

 

(A) Caterpillars have an innate tendency to move in the direction of gravity.

(B) Newly hatched caterpillars are unable to see in the dark.

(C) Newly hatched caterpillars move towards the strongest light source in the environment.

(D) Newly hatched caterpillars move toward the leaf bud nearest to them.

(E) The eyes of newly hatched caterpillars become less sensitive to light over time.

题干里说了caterpillar的两种行为，为什么答案是C而不是D呢

emilyhsieh

因為要support the statement given 就是後來的實驗敘述。

對了，想問你這邏輯的prep破解版要去哪裡下載？

emilyhsieh

至於第一題，因為題給兩個原因: killer whale or disease.既然不是disease 就可能是whale

coffeeid

感觉第一题的答案不是很充分啊，要解释的是SEA OSTER的DECLINE，不过确实其他答案都不好

http://forum.chasedream.com/dispbbs.asp?boardID=34&ID=245414&page=1

emilyhsieh

一起加油

ashleyyuan

            

題目已經說明很清楚,海獺數量減少的原因有兩個可能原因:疾病跟天敵(殺人鯨),題目結論推知是疾病的關係造成海獺數量減少,要推翻這個邏輯,必須找出除了疾病外的其他原因.

選項A已經很清楚題到造成海獺數量減少的其他原因,所以答案選A

ashleyyuan

                In
a recent experiment, a strong light source was placed at the bottom of
a tree, and caterpillars, after hatching, climbed downward. 題目已經跟你講了,底部光源會導致毛毛蟲往下爬而非往上爬,光源是造成毛蟲爬行的主要原因,答案C告訴你剛孵化的毛蟲會往光源方向爬去,與題目支持的理由相同,所以答案是C

coffeeid

谢谢楼上的。第二题中的(C) Newly hatched caterpillars move towards the strongest light source in the environment还是觉得很奇怪，即使说是Move towards the light source，怎么会得出来是strongest light source呢，还是想不通

再有想问问考试时前20题CR大概几道啊，这个部分是最不稳定的，怎么迅速提高呢

whitemint

因为和光有关.那就要用光的强度变化来检验咯....高中生物实验不都这么做的吗.~

我CR也郁闷。。。过3天就考试了。。

coffeeid

加油加油，希望前10题不要碰到CR