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题库 / Prep2012-CR-64
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?
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.
the earliest
因果
动作
b。不成立。原因有兩個。
一、利用negation。前面有小夥伴回答了，即使有這種食物，不代表西非人發現了，而且更不代表栽種了。所以就不能反駁文中的conclusion （know date（rice），know date（civilization））if 你negation這個條件。
二、即使存在這種食物，種植了，西非文明開始了。但是問題是為什麼在歷史上沒有record呢？題目前提條件告訴我們有紀錄的都是引入的食物。這個答案不能合理解釋這一點。
AB两者的取舍真的很容易让人中招，B只是说了有一种能够被培养成为主食的植物，但是这仅仅是有与没有，和有没有种植直接隔了十万八千里，即使有这种植物，当地人也不一定会去种植，所以只能说相关但是无法推论；而A就直接回答了问题：在rice和yam引进之前当地人没有种植其他可以作为主食的作物。
觉得是果因
前提：所有记录的西非的主食都是由别的地方进口（由rice和yams起） （果）
结论：rice和yams的进口时间就是农业社会开始时间 （因）
因果推理：选项内容必然和推断文段的前提有一定关系，找到语意上反驳的就可削弱；若选项描述为否定句，取非求加强亦可；
大半夜看题，愣是没读懂A什么意思……服了自己了，明明跟脑子里的reasoning一模一样
A. 西非人没开发过某种主食，一旦米和甘薯引进这种主食就不再种植了；取反则为有一种主食在米和甘薯之前种植过，削弱，正确
B. 没有一种植物是本土的，如果种植，能做主食；谈的是假设，取反为即使有，但也不一定种植，无法削弱结论，错；
体会一下B的if，是一种可能性，不能保证削弱
同样用negation technique, A： People in western Africa DEVELOPED staple crops that they stopped cultivating once rice and yams were introduced. 意思是western africa的人之前有种staple crops，不过在rice and yams were introduced的时候就停止了耕种了。说明在rice and yam引进前他们就已经开始了agricultural society, weaken原argument
为什么第二个不对？
B 说的是没有一种植物是本土的，如果种植，能做主食；聊的是假设，取反也比较弱，不能削弱结论；
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这一题的前提是什么啊，a选项感觉没看懂
因果