I think it will be much easier for us to understand choice A, if we change it to A. eople in western Africa HAD not develop staple crops that they stopped cultivating once rice and yams were introduced.
I think it will be much easier for us to understand choice A, if we change it to A. eople in western Africa HAD not develop staple crops that they stopped cultivating once rice and yams were introduced.
A. People in western Africa did not develop staple crops that they stopped cultivating once rice and yams were introduced. A项翻译为“当rice和yam引进后，西非人就没有发展之前种植的staple crops”。直译为 “西非人没有发展这些，当rice and yam被引入后，就停止种植的staple crops。”
A取反，如果还继续发展了之前的staple crops，那什么时候引进rice and yams就无法和最早的农业社会建立联系。
终于明白了！！！ 跟前面同学有点见解不同！！！
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.
大家看结论是：最早引进大米和yam的日期COULD 产生了农业社会。也就是说前面同学们说的那些什么充分必要条件并不是本体真正的问题所在。因为结论没说最早引入的时间就是农业社会开始的时间。真正的flaw在于ALL recorded staple crops 是那些大米和yam。亲们纪录的是最早的时间是那些引入的大米和yam。如果有一种农作物是主食但是在大米被引进后就不再种了，（也就是说可能时间比大米引进的时间早）然后这农作物也因不是大米也就没被纪录。大米引进后就不种了。这样的话那农业社会开始的时间不久可能天了么。也就削弱了结论了。那么B为什么不对呢，因为你没这主食在大米引进后就消失了（即暗含早于大米）从而削弱大米could 最早（the earliest)的结论！说白了就是结论说大米的引入可能是农业社会最早的开始日期。但事实上我们要排除也许农业社会可能由于某种未记录且停止发展的主食的存在而出现的时间更早的可能性！！！
今天看到一个人在manhattan关于B项的解释。Ron也说这种解释on target.
"On negation this statement becomes:
There are SOME plants native to western Africa that, if domesticated, could serve as staple food crops.
Even if there were/are some plants that are staple crops and are native to Western Africa, we don’t know whether these staple crops were planted before the plantation of rice/yams by the agricultural societies, or after staple crops rice/yams were introduced in Western Africa. If it was the former case then it would weaken the conclusion and hence can be a valid assumption. If it is the latter case, then it’s not going to affect the conclusion anyway. Since we don’t know of this information, so this can’t be an assumption - since an assumption is something that must be true for the conclusion to be valid."
即使有这种作物存在，我们也不能判定它的种植是在大米引入之前还是之后。如果是之前，那么就会削弱。如果是之后。那么对文章就没有影响。所以B项是要排除的。因为它的多向不确定性。
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发表于 2011-3-10 16:14:18
eople in western Africa HAD not develop staple crops that they stopped cultivating once rice and yams were introduced.
