跪求GWD-9-Q40解释！

audreyzhang2

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.

答案是A，查了以前NN的解答还是晕头转向。虽然用排除法做对了，但是还是觉得A有点问题。

个人认为A取非，只能说明在R和Y引进后，A people就不发展staple crops了，但并不能说明之前就没有staple crops了呀。

这道题CD上讨论的不多，是不是大家都觉得很好理解呀？受打击阿~

hughlv

从题干中可以归纳出这样几个信息：1）西非从来没有自己产生过staple crops。2）西非仅有的staple crops是rise和yams。3）当前的staple crops都是从外地引进的。

这里最大的假设就是rise和yams的历史就是西非staple crops的历史（否则establish了rise和yams的最早日期并不能确定staple crops的最早日期）。即在rise和yams之前从来没有过staple crops，即A)选项的意思。

对A取非的话，即表示在rise和yams引进之前西非人民就已经有发展staple crops了，从而导致无法根据rise和yams的引入时间来判断西非的staple crops的最早时间。lz的取非取错地方了，重点在引入rise和crops之前有没有发展staple crops，而不是引入之后有没有停止发展。

nysen

还是不懂，求解释~

camelo777

题目的结论是 discovering when rice and yams were introduced into western Africa

would establish the earliest date（注意是最早） at which agricultural societies could have arisen there. 然后文中有提到这个agricultural socieyies 存在的证据是有staple crops.  那么假设你是在削弱这道题的话，自然就会说在引进rice and yams之前，西非其实已经有staple crops了，或者已经开始发展种植了，这样的话，rice and yams的出现就不是最早（the earliest date）能够证明agricultural societies出现的了。
把上面的假设取非，你就得到了A选项

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.

nysen

题目的结论是 discovering when rice and yams were introduced into western Africa

would establish the earliest date（注意是最早） at which agricultural societies could have arisen there. 然后文中有提到这个agricultural socieyies 存在的证据是有staple crops.  那么假设你是在削弱这道题的话，自然就会说在引进rice and yams之前，西非其实已经有staple crops了，或者已经开始发展种植了，这样的话，rice and yams的出现就不是最早（the earliest date）能够证明agricultural societies出现的了。
把上面的假设取非，你就得到了A选项

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.

-- by 会员 camelo777 (2011/6/21 11:27:17)

可是这里用的是 once啊，取非A选项得到的是：一旦rice和yams被introduce，people就会develop ......

可这时候已经有rice和yam存在了，也能说明rice和yam是最早的staple crop（尽管有其他的staple crop），从而证明agricultural societies出现的时间。

camelo777

A的意思是在rice和yams被introduce之前，People in western Africa没有 develop staple crops 然后因为这个rice和yams被引进了就停止了.

取非的话就是在rice和yams被引进之前，他们就develop staple crops了，可能我说的不是很清楚，你自己好好看看A选项，理解一下

nysen

了该！多谢了~