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.
有做过GWD，也木有看过GWD的分析，不知道这么理解对不对~
小鹿怎么觉得这个B选项是个已知的前提呢？passage里面说，“All the recorded staple crops grown in western Africa were introduced from elsewhere, beginning, at some unknown date, with rice and yams. ”感觉明确说出了B选项的东西，所有主要作物都从外地引进，就等于B选项的本地没有native的主要作物
A选项说实话单让小鹿读的话可能读不太明白，不过对这道题的想法是这样的：
前提1：没有主要作物，农业社会不可能存在
前提2：所有在西非地区的主要作物都是从外地引进的，以rice和yams为始
结论：知道rice和yams的引进时间，就能知道西非地区的农业社会最早可能从什么时候开始了
这么分析完以后再看A选项，小鹿会这么理解：文章的意思是从开始发展主要作物开始，农业社会可能就已经开始了，原文说了西非地区several不是主要作物的作物，但是没有说当时并没有在尝试发展主要作物。直到引进了新的主要作物——rice和yams，西非地区放弃了之前他们在尝试发展的主要作物，转而种植rice和yams。估计出题人自己都觉得这逻辑链有点牵强，所以出题时候又回过头在“All the recorded staple crops grown in western Africa
were introduced from elsewhere, beginning, at some unknown date, with rice and yams.”这句话里面开头的staple crops前面加了一个recorded，被记载的。也就隐含了可能存在没被记载的主要作物，没被记载的原因是因为stop cultivating了，A选项~
个人看法噢，open to discuss作者: shelvey 时间: 2012-7-13 06:39
B is wrong since it is too strict.
Remember in Necessary Assumption questions, the correct answer is normally soft, less strict. When you see modifiers such as ALL, Must, No, Never, Always, that is probably a wrong answer choice.作者: xiaoguolulu 时间: 2012-7-13 20:36
谢谢两位的回答，B选项我好像有些明白了，因为argument中“All the recorded staple crops grown in western Africa were introduced from elsewhere, beginning, at some unknown date, with rice and yams.”，而且B选项也过于绝对了，其实WA有没有发展可以用来当做staple food 的crops其实根本无关。
但是A选项到底是什么意思呢？我用Negation还是不明白~~~Sdcar大神能不能帮忙解释一下
People in western Africa did not develop staple crops （that they stopped cultivating once rice and yams were introduced.）
这个that的定语从句到底是什么意思？我觉得这题可以发去语法区问问了~作者: shelvey 时间: 2012-7-14 15:53
Conclusion: when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there.
A) just makes sure that before rice and yams, there were NO other staple food in Western Africa.作者: xiaoguolulu 时间: 2012-7-15 07:53
Got it! Thank you for your great kindness!!!作者: annieview 时间: 2012-7-15 21:35
或许可以这么理解(?):
A. People in western Africa did not develop staple crops that they stopped cultivating once rice and yams were introduced.
理解为：
people in western A did not develop staple crops ( that they stopped cultivating)
(once rice and yams were introduced).
即
A 的人民们就不种主食了，神马样的主食呢？是“一旦rice and yams被引进之后，他们停止种植的主食”
神马叫做rice and yams引进后就不种植的主食？
其实就是 在rice and yams引进之前种的主食
so
代入原句
A的人民不种 rice and yams引进之前的主食
即NN所说 rice and yams之前 木有种植主食 作者: xiaoguolulu 时间: 2012-7-16 06:24
谢谢解释~~~你这么一说就跟清楚我就更清楚了！！！
这题真是的，敢不敢再把选项出得难读懂啊！！！！！！！！！
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