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题库 / DaQuan-CR-3709
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.
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。
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）
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
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；登录 或 注册 后可以参加讨论