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标题: 请教一题 [打印本页]

作者: geniuswang 时间: 2009-6-6 20:01
标题: 请教一题

GWD-9-Q40:

Agricultural societies cannot exist without staple crops. Several food plants, such as kola and okra, are known to have been domesticated in western Africa, but they are all supplemental, not staple, foods. All the recorded staple crops grown in western Africa were introduced from elsewhere, beginning, at some unknown date, with rice and yams. Therefore, discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there.

Which of the following is an assumption on which the argument depends? A

People in western Africa did not develop staple crops that they stopped cultivating once rice and yams were introduced.
There are no plants native to western Africa that, if domesticated, could serve as staple food crops.
Rice and yams were grown as staple crops by the earliest agricultural societies outside of western Africa.
Kola and okra are better suited to growing conditions in western Africa than domesticated rice and yams are.
Kola and okra were domesticated in western Africa before rice and yams were introduced there.

正确答案是A，请问解题思路是什么呢？可以用排除法把其他四个枪毙，但是A：首先语句读不通；其次逻辑上我也不明白啊，请达人出手！！

作者: geniuswang 时间: 2009-6-6 21:26
ding

作者: laofan3000 时间: 2009-6-7 04:00
All the recorded staple crops 是 rice and yams.所以只要知道when rice and yams were introduced into就知道agricultural societies开始的时间，A就排除了在引进rice and yams没有其他的staple crops的存在。
A取反,如果在引进rice and yams有其他的staple crops 比如corn的存在，只是在引进了rice and yams后，不再耕作了，那agricultural societies开始的时间应该是corn开始种植的时间

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