求教一道题~

sgzw37

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.
                                                                                                                                                                                    Answer: A
看完题目lz以为只要考虑在rice来之前没有agriculture的萌芽就行了，但是找不到对应选项@-@
求助大神帮解答下我的小思路对不对，还有解释下A这个正确答案是怎么理解的0.0 谢谢~~~

sgzw37

就木有人来么

militant001

前提1：staple crops出现后才有agricultural society;
前提2：最早【 被记录】的staple crops是rice and yams;
方案：通过rice and yams的引入时间可推出agricultural society最早出现的时间

这个argument的漏洞：是否有没被记录的staple crops出现在rice and yam之前？

选项A说rice and yams之前没有其他staple crops，因而补上了这个漏洞。

愚见，仅供参考

sgzw37

militant001 发表于 2014-3-9 13:32
前提1：staple crops出现后才有agricultural society;
前提2：最早【 被记录】的staple crops是rice and ya ...

同意你的分析！然后我看A选项就觉得奇怪：如果说stopped cultivating，那么之前就是有staple crops，这样不就weaken了么?