单选题 Fresh potatoes generally cost about $2 for a 10-pound bag, whereas dehydrated instant potatoes cost, on average, about $ 3 per pound. It can be concluded that some consumers will pay 15 times as much for convenience, since sales of this convenience food continue to rise.
Which of the following, if true, indicates that there is a major flaw in the argument above?

A、 Fresh potatoes bought in convenient 2-pound bags are about $1 a bag, or 2 1/2 times more expensive than fresh potatoes bought in 10-pound bags.
B、 Since fresh potatoes are 80 percent water, one pound of dehydrated potatoes is the equivalent of 5 pounds of fresh potatoes.
C、 Peeled potatoes in cans are also more expensive than the less convenient fresh potatoes.
D、 Retail prices of dehydrated potatoes have declined by 20 percent since 1960 to the current level of about $3 a pound.
E、 (E) As consequence of labor and processing costs, all convenience foods cost more than the basic foods from which they are derived.

【正确答案】 B

【答案解析】[解析] 如果新鲜土豆有80%的水分，每磅脱水土豆相当于5磅新鲜土豆，如(B)所说，那么段落推理结论的“15倍的价格”便必不成立，所以(B)正确；(A)是在“2-pound bags”与“10-pound bags”之间做了无关比较；(C)是在“peeled potatoes”与“the less convenient fresh potatoes.”之间做了无关比较；(D)是无关答案；(E)是一个真理，但与上面推理无关。牢记：逻辑推理题是让我们找一个与上面推理有关且能实现问题目的的答案，而不仅仅是让我们找一个可以作为真理的答案。