Escalating worldwide demand for corn is expected to cause the market price of corn to rise sharply and remain high. Although corn is extensively used as feed for livestock, livestock feed accounts for only a small fraction of the retail price of meat. Therefore, the increase in corn prices is very unlikely to produce any comparable long-term increase in the retail price of meat.

Which of the following, if true, most seriously weakens the argument?


The cost of shipping and handling meat has also risen sharply.

Livestock producers who currently use corn to feed their livestock have the option of switching to other kinds of feed.

The rising cost of feed is leading some livestock producers to leave the business, thereby reducing the future supply of meat.

Worldwide demand for grains other than corn has also increased.

The price of corn affects the retail price of a variety of other food products more than it affects the price of meat.

考题讲解

情景:近些日子的收成不好。纵然玉米价格上涨且玉米是喂养畜牧动物的粮食,但是喂养费仅仅占据肉类零售价很小的一部分,所以,玉米价格的上涨不太可能带来肉价的上涨。

推理:

前提:玉米价格上涨且玉米是喂养畜牧动物的粮食,但是喂养费仅仅占据肉类零售价很小的一部分
结论:玉米价格的上涨不太可能带来肉价的上涨

答案预估:

那些“玉米价格上升不会导致肉价上升”的其它必要条件(常理上能保真推理出的一切结果)不存在。

选项分析:

A选项:肉类的运输费和处理费也上涨了很多。本选项给出了肉价会上涨的两个可能的原因,但其和玉米价格是否会导致肉价上升无关。

B选项:现在把玉米作为喂养粮食的畜牧业主可以选择其它的粮食喂养家畜。无论业主选择什么东西来喂养家畜,都不能反驳玉米是否会带来肉价的上升这个结论。

C选项:Correct. 上涨的喂养粮食价格会导致一些畜牧业主离开这个行业,因此导致肉类供给的缺乏。很明显,玉米价格上升不会导致肉价上升的一个必要条件是玉米价格的上升不会让供给下降,否则肉价必然会有变动。因此,本选项相当于告诉了我们结论的一个必要条件不存在。


D选项:对于除掉玉米的粮食的需求上涨了。无论玉米的需求量是否增加,其均与玉米和肉价之间的关系无关。

E选项:
肉类零售价格比其他产品的零售价格更不容易受到玉米价格的影响。无论玉米价格会影响什么样的产品,其均不是结论的必要条件。

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