GWD逻辑题求解答！HELP!!

gmat考750

GWD6 Q21
Scientists have made genetic modifications to cotton to increase its resistance to insect pests.  According to farmers' report, the amount of insecticide needed per acre to control insect pests was only slightly lower for those who tried the modified seed than for those who did not.  Therefore, since the modified seed costs more than ordinary seed without producing yields of higher market value, switching to the modified seed would be unlikely to benefit most cotton farmers economically.

Which of the following would it be most useful to know in order to evaluate the argument?

	Whether farmers who tried the modified cotton seed had ever tried growing other crops from genetically modified seed
	Whether the insecticides typically used on ordinary cotton tend to be more expensive than insecticides typically used on other crops
	Whether for most farmers who grow cotton it is their primary crop
	Whether the farmers who have tried the modified seed planted as many acres of cotton, on average, as farmers using the ordinary seed did
	Whether most of the farmers who tried the modified seed did so because they had previously had to use exceptionally large quantities of insecticide

答案是D，
不知道如何排除E，感觉E好像也有关
而D选项说的是亩数，题里面给了每亩平均，不知道D如何与题目相关

求解答！

谢谢！！

hanshipeng

选B

gmat考750

HELP!~~~

gmat考750

选B

-- by 会员 hanshipeng (2011/8/23 21:27:23)

啊？答案是D啊？

gmat考750

HELPHELP~~

bluesolo

题目说： amount of insecticide needed per acre 几乎没变。
所以推论说：由于转基因的种子贵，而且平均亩数用的杀虫剂没变，所以不划算。

其实题目tricky的地方就在于amount of insecticide needed per acre。
由于TTL cost of insecticide 是最终需要衡量的标准
而TTl amont of insecticide = amount of insecticide needed per acre* acre
所以只有当种转基因棉花和正常棉花的亩数没变的时候，才能推论出来说农药的总成本没变，从而种转基因的TTL cost 就高了，所以不划算。

B和E都是无关选项。我的经验是题干中如果比较A和B，那么正确选项里也应该是涉及到A和B的内容。

gmat考750

题目说： amount of insecticide needed per acre 几乎没变。
所以推论说：由于转基因的种子贵，而且平均亩数用的杀虫剂没变，所以不划算。

其实题目tricky的地方就在于amount of insecticide needed per acre。
由于TTL cost of insecticide 是最终需要衡量的标准
而TTl amont of insecticide = amount of insecticide needed per acre* acre
所以只有当种转基因棉花和正常棉花的亩数没变的时候，才能推论出来说农药的总成本没变，从而种转基因的TTL cost 就高了，所以不划算。

B和E都是无关选项。我的经验是题干中如果比较A和B，那么正确选项里也应该是涉及到A和B的内容。

-- by 会员 bluesolo (2011/8/23 22:15:36)

豁然开朗，谢谢LS!

qilu8989

大家确认一下，我做是选D的，但答案是B，所以我印象特别深刻！！！难道答案是D吗？

bluesolo

那你能解释一下B的逻辑是什么么？

衡量转基因和非转基因棉花种植的成本，为什么会涉及到other crop的内容呢？？？

hanshipeng

我觉得选B，虽然B提到了other crop，貌似无关，但是仔细读一下，ordinary seed比其他crop农药都贵，其他crop就可以认为包括modified。
这道题关键是第一，转基因比非转基因节省用药量不显著，但是也有那么slightly fewer。另一个就是种子成本较非转基因高。关键就是节省农药的那点钱能否弥补种子成本高，从而得到是否经济（题中提到，两种棉花产值一样，即revenue一样）。那么自然就把重点放在农药的价格上了。
再来说说答案D，亩数不是关键的，如果转基因成本高于非转基因，种一亩转基因都是不经济的，反之，如果转基因划算，种转基因越多越经济。
我坚持选B