求解一道CR题

eliasfan

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

eliasfan

The answer is A ,but I want to know why not C !
reason :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.
conclusion:until the cost of extracting uranium from seawater can somehow be reduced, this method of obtaining uranium is unlikely to be commercially viable

C has point out that the cost will be reuced

lonelyorchid

注意原文的逻辑，如果从seawater中提取urinium要比在市场上的价格贵，那么就不会从seawater中提取urinium。要评价的内容是由于提取的成本降低而产生的后果。所以要评价，就要看是否只会有着一个结果。即A 是否市场会涨价。如果市场不涨价，那么只有通过cost降低，如果市场涨价，那么cost不变甚至升高都仍然会使得结论成立。

eliasfan

也就是说A铁定成立，而C只有在COST降到低于市场价时才成立？