请教一道题，急

pygmysog

其实这道题我读的时候没看太懂，但是用排除法也得到了C，楼主可以借鉴一下。
Grazing livestock on public land in the western United States is not causing widespread environmental damage in the region, since if it were, the condition of that land would not be improving.
However, only 14 percent of public land in the area today is considered to have inadequate vegetation cover and, therefore, to be in poor condition, while in the 1930's, 36 percent had inadequate vegetation cover.

Which of the following, if true, most seriously weakens the argument above?

A) In the western United States, private land is typically more lush than public land, and cattle that graze on prive land can be fattened more quickly.
[irrelevant, 根本就没拿private 和 public 作比较]
B) Since the 1930's, recreational users of public land in the western United States have caused more environmental damage than have the cattle grazing there.  [irrelevant, 文章既没题recreational也没说要拿他们和grazing比较]

C) During the 1930's, an unusually destructive dtrought prevailed thoughout the region where most public lands in the western United States are located.  [觉得差不多是这个意思，可以先放着，要是后面还有排除不了的，再回过头来看]

D) Ranchers who use public land in the western United States pay only a fraction of what is paid by those who lease comparable private land for grazing. [irrelevant, 没提钱的事儿，也没说要lease]

E) The amount of land purchased by the United States government since the 1930's is relatively insignificant. [扯得更远了]