gmat逻辑问题

题目

gmat逻辑问题
7.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 a 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) As a consequence of labor and processing costs all convenience foods cost more than the basic foods from whic

答案

题***意思是一种方便的脱水土豆比新鲜土豆价格贵15倍,因此,这种方便的脱水土豆销量上升了,说明消费者愿意为这种方便付出15倍的价格. 问题是这种说法的错误在哪. A、方便的新鲜土豆价格是1美元2磅,比单纯的新鲜土豆贵1.5倍.这个方便的新鲜土豆是一个无关条件,题目中没有提到这个东西.因此,这种价格的比较也没有意义,这个选项是无关选项. B、由于新鲜土豆含有80％的水份,因此一磅脱水土豆等于5磅新鲜土豆.这说明生产脱水土豆的成本比新鲜土豆要高,那么消费者为了方便的脱水土豆支付高价,不仅仅是因为它方便,同时也是因为它的成本高.即：消费者并不仅仅是因为方便就支付了15倍的高价.这正好是题目论点的错误所在.