求助 Og语文分册cr22~ farmer用水的对象到底是什么？

miffyflysky

22. In the arid land along the ColoradoRiver, use of the river's water supply is strictly controlled: farms along the river each have a limited allocation that they are allowed to use for irrigation. But the trees that grow in narrow strips along the river's banks also use its
water. Clearly, therefore, if farmers were to remove those trees, more water would be available for crop irrigation.
Which of the following , if true, most seriously weakens the argument?
(A) The trees along the river's banks shelter it from the sun and wind , thereby greatly reducing the amount of water lost through evaporation .
(8) Owners of farms along the river will probably not undertake the expense of cutting down trees along the banks unless they are granted a greater allocation of water in return .
(C) Many of the tree species currently found along the river's banks are specifically adapted to growing in places where tree roots remain constantly wet.
(0) The strip of land where trees grow along the river's banks would not be suitable for growing crops if the trees were removed.
(E) The distribution of water allocations for irrigation is intended to prevent farms farther upstream from using water needed by farms farther downstream.

对象是use of river's water supply
farmer用的水应该是river中的一部分  跟river中总水量没有关系吧   那就应该跟tree保不保护water没关系了  反正只是用水用的是一个量 而不是比例
而且tree在保护水分流失的同时也在用水呀  没有说净用水量为多少呀
我是这样理解的  所以觉得不该选a  求教育呀!!!

miffyflysky

噢。 就是说a中的tree导致总水量增加是一个整体，一个前提，是一定正确的，懂了，谢了哈亲

miffyflysky

很简单  举个例子

假设2户人家 河水一共200  浇树要用20 剩下180可以浇田 每户90

砍树后 蒸发40 剩下160 每户80

所以 不该砍树

-- by 会员 HarrisZheng (2012/9/28 16:41:28)

-- by 会员 HarrisZheng (2012/9/28 16:41:55)

可是它没说是按这样的方法来分的呀。要是只从200中拿100给农民灌溉，不管总水量多少那就说不通了呀？。

HarrisZheng

很简单  举个例子

假设2户人家 河水一共200  浇树要用20 剩下180可以浇田 每户90

砍树后 蒸发40 剩下160 每户80

所以 不该砍树

-- by 会员 HarrisZheng (2012/9/28 16:41:28)

HarrisZheng

很简单

ruudarly

你有点钻牛角尖了哈，你说用水量跟保护不保护tree没有关系是否定了前提，而CR里永远都承认前提是正确的，也就是说一定有关系。
我做这题的思路是这样的，假设farmer每一户分一块地，每块地旁边有树，而砍不砍树直接导致自家用水量的多少，所以如果树木的作用是保护水资源，那么对自家肯定有益的