老prep cr1 16

chaseconsult

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

chaseconsult

说错了，正确答案为A，哎，被逻辑搞得已经头晕脑涨了

Benite

A is correct.
C is irrelevant.The conclusion is:until the cost of

extracting  uranium from seawater can somehow be

reduced,this method would not be commercially viable.
We need to know weather only after the cost decreases, the

method would be commercially.C can't help us to evaluate the

conclusion.
A: If the situation is ture, the method of extracting

uranium from seawater would be used though its cost would

not decrease, because the method of extracting uranium from

mine would increase, resulting in the cost of extracting

uranium from seawater larger than the cost of from mine.

chaseconsult

一语惊醒梦中人啊，偶好傻，对啊，是要评价conclusion是否可行，不是评价conclusion里的内容是否可行，多谢了。