单选题 Scientists have rediscovered certain food crops, once commonly cultivated in the New World, which contain more protein per pound than do current staple food crops such as rice and wheat. Scientists claim that cultivation of these crops could greatly benefit densely populated countries that have low per-person calorie intake and inadequate source of protein.
Which of the following, if true, casts the most serious doubt on the claim made above?

A、 The average yield per acre of the rediscovered crops is substantially less than that of the current staple food crops.
B、 Many important food crops, such as tomato, originated in the New World.
C、 Wheat yields more protein per pound than does rice.
D、 The rediscovered crops have more caloric per pound than do current, staple food crops.
E、 (E) As few as 20 different food crops provide the bulk of the planet's food supply.

【正确答案】 A

【答案解析】[解析] 本题根据每磅这种谷物的蛋白质含量高于其他主要农作物而做出这种谷物对人口稠密、人均摄入量低和蛋白质来源不足的国家有好处的结论。很显然本题的结论是以这种谷物的产量比其他主要农作物高或至少不能比其他农作物的明显地低为前提。(A)指出“新发现的农作物的每亩平均产量比目前粮食作物产量低得多，从而严重地削弱了结论所依赖的一个前提条件，因此(A)正确。(B)和(E)为无关选项；(C)和(D)引入新的比较，所以也都为错误选项。