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
正确答案为C，但我觉得很奇怪啊，最后说除非从海中提取U的成本能够降低，否则就不会使用这个方法，那么C不是正好给出了答案吗？如果可以有这种技术，那么从海中提取就可行，如果没这种技术，那么就不可行？我觉得A有道理，C同样没错啊，求解释，这个问题大家都会吗？为何搜不到同个问题的帖子……，呜呜