请教各位CR大神 关于verbal的一道题

lylove47

56. Gortland has long been narrowly self-sufficient inboth grain and meat. However, as per capita income in Gortland has risen towardthe world average, per capita consumption of meat has also risen toward the worldaverage, and it takes several pounds of grain to produce one pound of meat. Therefore,[url=]since per capitaincome continues to rise, whereas domestic grain production will not increase,Gortland will soon have to import either grain or meat or both[/url]

Which of the following is an assumption on which the argumentdepends?

[url=](A)[/url]The total acreagedevoted to grain production inGortland will not decrease substantially.

(B) The[url=] population [/url]of Gortland hasremainedrelatively constant during the country's years ofgrowing prosperity.

(C) The [url=]per capita consumption [/url] of meatin Gortlandisroughly the same across all income levels.

[url=](0)[/url]In Gortland,neither meatnor grain is subject togovernment price controls.

(E) People in Gortland who increase theirconsumption ofmeat will not radically decreasetheir consumption of grain[url=]E [/url]

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正确答案是E

对B选项存在疑惑，听了论坛里整理的录音什么的还是没有解答我的疑惑，请大家来讨论一下。

B选项：在G国家财富增长的这几年里，G国家的人口保持不变。我认为是一个所需的假设。因为文中说的是人均消费肉会增长，而G国家的粮食产量（总量）不会增加，所以如果G国人口数量大幅减少，那么可能所需的总肉量不升反降也有可能啊。所以B是一个所需assumption。

请各位大神来解答一下

lylove47

想来想去，总量是应该与平均数和数量有关的吧。所以人口数也是一个影响因素。

keruan

你最好重新编辑下，没空格  这题是necessary assumption，也就是要你选必须是对的那个，否定 B population not remain constant 人口可能多也可能少，可能少1%也可能少90%，但是具体是哪个你不知道。也就是说即使population not remain constant 结论Gortland will soon have to import either grain or meat or both也不一定不成立，因此B不是必须正确的。

lylove47

keruan 发表于 2014-8-27 17:20
你最好重新编辑下，没空格  这题是necessary assumption，也就是要你选必须是对的那个，否定 B population  ...

谢谢谢谢，你这样解释B，取非之后是不能一定weaken结论，我能想通B不是正确答案。但是E选项，取非之后，消费肉增多的那一群人will radically decrease their comsumption of grain（总量概念）. 如果这个时候，全国总人数增加了，还是需要import grain or both，就不会weaken结论了。劳烦再解释一下呢？是不是我想太多了，但是我觉得这道题不太严谨。

keruan

你自己都说了如果人口总数增加，然后才怎样。这其实就是你自己给题目增加了一个条件，如果人口增加了。而B之所以可以提到人口增加还是减少什么的，是因为这都叫population not remain constant