求教：PREP中有关sea otters的题目

cindydai0923

   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.

为什么答案选A呢?我没想明白...呼唤NN~

kitebird

题目提供了两种原因：There are two plausible explanations for the decline: predation, possibly by killer whales, or disease.

并说是由于disease，而问题要求weaken

A说明因为disease,seals and sea lions 都病了，所以Killer whales in the North Pacific 的食物就减少了，只能 seek out other prey，也就是sea otters。就削弱了sea otters是因为diseas这个结论。

cindydai0923

哦哦，我转过来啦，谢谢，赫赫

CCatherine

这是属于将原因跟结果倒过来说的方式么？

12711399

为什么B不对？ SEA OTTER直接走了。。。那么说明数量的降低不是病死的 而是迁移造成的 直接毁灭了这个CONCLUSION

A的话 seek out other prey  OTHER PREY可以是其他海洋东部，不一定是要SEA OTTER

spoon0212

12711399 发表于 2012-12-7 17:37
为什么B不对？ SEA OTTER直接走了。。。那么说明数量的降低不是病死的 而是迁移造成的 直接毁灭了这个CONCL ...

同问同问，好像没有人回答啊

elsachialee

spoon0212 发表于 2013-7-9 10:15
同问同问，好像没有人回答啊

我觉得。。探讨下。。

文中需要weaken的是结论，结论是，sea otter的数量减少是因为生病。。。所以需要找出他因，其实是什么其他因素造成了数量减少。
A说 是这个killer whales，当它没有东西吃的时候，就来吃sea otter了。
B中，说没有indication是不是sea otters migrate到其他地方去了。那么如果是，是weaken，可是也可以不是，sea otters木有去其他的地方。那么就不是weaken了。

再啰嗦自我分析下，
weaken和strengthen要特别注意前提和结论，是不能质疑前提的。
这个题目当中前提很多
1. sea otter的数量减少。
2.两种可能，一种是killer whale，一种是disease。
3. seal和sea lion数量减少，是因为disease。

其实我一开始就把A排除了，因为觉得是无关，以为题目问题需要关注的是disease和sea otters之间的关系。其实只要找出它因，什么其他原因造成了sea otter数量减少，且不违背前题的条件下。A刚好是很符合前题的，因为本来就是有猜测，killer whale就是要吃sea otter的。再有，seal和sea lion都生病，killer whale吃不到他们了，所以只能来吃sea otter了。

CD!

12711399 发表于 2012-12-7 17:37
为什么B不对？ SEA OTTER直接走了。。。那么说明数量的降低不是病死的 而是迁移造成的 直接毁灭了这个CONCL ...

因為沒有攻擊到紅字的部分
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.

争取一次就过

12711399 发表于 2012-12-7 10:37
为什么B不对？ SEA OTTER直接走了。。。那么说明数量的降低不是病死的 而是迁移造成的 直接毁灭了这个CONCL ...

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.
没有迹象表明，他的减少和迁徙有关。
可能你漏看了no吧

争取一次就过

12711399 发表于 2012-12-7 10:37
为什么B不对？ SEA OTTER直接走了。。。那么说明数量的降低不是病死的 而是迁移造成的 直接毁灭了这个CONCL ...

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.
没有迹象表明，他的减少和迁徙有关。
可能你漏看了no吧