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.
B. There are no plants native to western Africa that, if domesticated, could serve as staple food crops.
C. Rice and yams were grown as staple crops by the earliest agricultural societies outside of western Africa.
D. Kola and okra are better suited to growing conditions in western Africa than domesticated rice and yams are.
E. Kola and okra were domesticated in western Africa before rice and yams were introduced there.
正确答案是A 可是看不懂A是什么意思？我理解的是 西非的人就没有发展他们停止种植的主要作物， 一旦大米和山药被引进。
staple crops that they stopped cultivating 是不是说明他们在大米和山药引进前 就已经有主要作物了？
请求解答作者: mudiduanger 时间: 2010-12-17 06:47
我刚开始也选的B
There are no plants native to western Africa that, if domesticated, could serve as staple food crops.
可是后来又觉得和原文的 All the recorded staple crops grown in western Africa were introduced from elsewhere
意思重复作者: pilipala711 时间: 2010-12-19 06:55
我认为可以这样理解A：当大米和山药一旦被引入西非之后，那里的人才开始开发主要农作物了，而之前呢？是staple crops that they stopped cultivating 。题目给出的结论是，发现大米和山药的引入时间就可以确定农业社会的最早时间，题目问Depends，而题干给出了一个先决条件，Agricultural societies cannot exist without staple crops，也就是说有了staple crops才有Agricultural societies，那么就是找staple crops出现的时间就可以了，A在说staple crops的出现时间
B没有native plants和staple crops 是两回事
C是说不再西非范围内的staple crops ，而题目问在这个范围内
D、E都是supplemental, not staple, foods.作者: natalietong 时间: 2010-12-19 20:52
A 取反：在引进rice and yam前，西非人develop了自己的staple crops
但引进之后，停止了。
明显消弱了结论，想用 rice and yam来确定，但没想到之前有staple crops只不过引进 rice and yam停止作者: youngerlee 时间: 2010-12-20 19:57
当大米和山药一旦被引入西非之后，那里的人才开始开发主要农作物了,A是怎么看出这个意思的呀
A取非能削弱 可是我感觉不取非也能削弱。。。因为staple crops that they stopped cultivating
要是把that从句括起来就好了
我还有一种想法 不知道对不对 ：
就是西非人原来种过staple crops 但是没成功 stop 了 但是他们没有继续develop 后来大米和山药引进了
就说明大米和山药是最早的的了
