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题库 / Prep2007E1-CR-16
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?
Whether the uranium in deposits on land is rapidly being depleted
Whether most uranium is used near where it is mined
Whether there are any technological advances that show promise of reducing the cost of extracting uranium from seawater
Whether the total amount of uranium in seawater is significantly greater than the total amount of uranium on land
Whether uranium can be extracted from freshwater at a cost similar to the cost of extracting it from seawater
因：成本不能降下来；
果：海水提铀商业不可行；
评估方向：
（1）攻击结论：它果/干扰因，如有干扰因素X，使成本虽不能降，但商业上仍可行；
（2）攻击前提：因果无关，成本降不降和海水提铀商业可不可行无关。如陆地上铀用完了，海水提铀是大势所趋，和成本无关。
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