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. eople in western Africa did not develop staple crops that they stopped cultivatin g
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
This is an assumption question and you can use the so-called deny test, i.e., negate a choice, see whether the original argument will fall apart; if so, the choice is a necessary assumption of the argument.
The opposite of A is "People in western Africa did develop staple crops that they stopped cultivating once rice and yams were introduced." If this is true, the conclusion "discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there." will fall apart, because agricultural societies could have established before the introduction of rice and yams. Therefore, A is a necessary assumption.
The opposite of A is "People in western Africa did develop staple crops that they stopped cultivating once rice and yams were introduced." If this is true, the conclusion "discovering when rice and yams were introduced into western Africa would establish the earliest date at which agricultural societies could have arisen there." will fall apart, because agricultural societies could have established before the introduction of rice and yams. Therefore, A is a necessary assumption.
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发表于 2004-7-19 10:25:00
eople in western Africa did not develop staple crops that they stopped cultivatin g 
我选B，我觉得题目只叙述了记录在案的情况，假设应把可能的情况排除掉
楼主
