prep16,没搜到旧帖，请NN帮忙

ruimiss

Most of the world's supply of uranium currently comes from mines.  It is possible to extract uranium from seawater, but the cost of doing so is greater than the price that uranium fetches on the world market.  Therefore, until the cost of extracting uranium from seawater can somehow be reduced, this method of obtaining uranium is unlikely to be commercially viable.

Which of the following would it be most useful to determine in evaluating the argument?

(A) Whether the uranium in deposits on land is rapidly being depleted
(B) Whether most uranium is used near where it is mined
(C) Whether there are any technological advances that show promise of reducing the cost of extracting uranium from seawater
(D) Whether the total amount of uranium in seawater is significantly greater than the total amount of uranium on land
(E) Whether uranium can be extracted from freshwater at a cost similar to the cost of extracting it from seawater

答案是A,我选的是C...不明白啊，我讨论是挖海里的，和你陆地上有多少有啥关系啊？就算你陆地上有很多，可是还是没有解决我如何挖海里的问题啊。。。？？？请教请教~~还是说我理解错误？

ruimiss

！啊。。sorry各位，我找到旧帖了 ~~~~~~忽略这贴吧~~~~~