OG12，CR的43题，不是很懂，求解答

腹黑男

43. Installing scrubbers in smokestacks and switching to cleaner-burning fuel are the two methods available to
Northern Power for reducing harmful emissions from its plants. Scrubbers will reduce harmful emissions more
than cleaner-burning fuels will. Therefore, by installing scrubbers, Northern Power will be doing the most that
can be done to reduce harmful emissions from its plants.
Which of the following is an assumption on which the argument depends?
(A) Switching to cleaner-burning fuel will not be more expensive than installing scrubbers.
(B) Northern Power can choose from among various kinds of scrubbers, some of which are more effective
than others.
(C) Northern Power is not necessarily committed to reducing harmful emissions from its plants.
(D) Harmful emissions from Northern Power’s plants cannot be reduced more by using both methods together
than by the installation of scrubbers alone.
(E) Aside from harmful emissions from the smokestacks of its plants, the activities of Northern Power do not
cause signi?cant air pollution.


答案选的是D，这是为什么呢？OG上面的解释我觉得有些模棱两可，各位麻烦在帮我解释下吧，对OG答案接受不能呀。

sdcar2010

Necessary assumption. Use negation.

If you negate D), you have:
Harmful emissions from Northern Power’s plants CAN be reduced more by using both methods together than by the installation of scrubbers alone.
If that is the case, then the conclusion "by installing scrubbers, Northern Power will be doing the most that can be done to reduce harmful emissions from its plants" is wrong since, apparently, there is a better reduction method by combined the two methods together.

Hence, D) is the necessary assumption.

腹黑男

Necessary assumption. Use negation.

If you negate D), you have:
Harmful emissions from Northern Power’s plants CAN be reduced more by using both methods together
than by the installation of scrubbers alone.
If that is the case, then the conclusion "by installing scrubbers, Northern Power will be doing the most that
can be done to reduce harmful emissions from its plants" is wrong since, apparently, that is a better reduction method by combined the two methods together.


Hence, D) is the necessary condition.

-- by 会员 sdcar2010 (2011/9/1 11:07:57)

3Q，我发现是我自己把D的意思理解错误了，谢谢啦