CXD逻辑6,N哥请进!√

The problem that environmental economics aims to remedy is the following:people making
economic decisions cannot readily compare environmental factors,such as clean air and the
survival of endangered species,with other costs and benefits.As environmental economists
recognize,solving this problem requires assigning monetary values to environmental
factors.But monetary values result from people comparing costs and benefits in order to
arrive at economic decisions.Thus,environmental economics is stymied by what motivates
it.if the considerations advanced in its support are true,the passage's conclusion is supported
论证过程：(A)做经济决策时不能考虑环境因素的成本收益——(B)解决问题需要赋予环境因素货币价值——(C)做经济决策时考虑成本收益才能算出货币价值。
结论：(C)和(A)自相矛盾。
a.strongly,on the assumption that monetary values for environmental factors cannot be
assigned unless people make economic decisions about these factors.
如果上述论证过程是对的，那么结论也是对的。(见红字部分分析)
b.strongly,unless economic decision-making has not yet had any effect on the things categorized as environmental factors.
不相关选项。题目中没有提到经济决策对环境问题是否造成影响。
c.at best weakly,because the passage fails to establish that economic decision-makers do not by and large take adequate account of environmental factors
错误选项。“文中没有说明经济决策者通常不会考虑环境因素”。而事实上，通篇都在说环境因素。
d.at best weakly,because the argument assumes that pollution and other effects on environmental
factors rarely result from economic decision-making.
错误选项，“rarely result from”——文中根本就没有这个假设
e.not at all,since the argument is circular,taking that conclusion as one of its premises.
错误选项，“not at all”这句话不对，但since the argument is circular,
taking that conclusion as one of its premises是对的，文中的错误正是循环引用。

这道题也把我搞懵了，但其实想想BCDE很容易排除，A的正确性也很明显。GMAT逻辑题往往是那种容易读懂句子反而不好选，像这种特别抽象的，确实比较好选答案。

这道题在GMAT里可能算是高分题了，题目句子长，选项的句子也长而且比较难理解准确。N哥们解这道题时要细仔了啊。现在我把答案也说了A。可以的话，请N哥们把A为什么正确和其它四项为什么不选的理由也讲一下吧。