A and B says challenging an assumption
which assumption? All should be premise and fact. Seeking for expert comment...

What's the correct OA A or B . Experts please reply ?

Environmentalist: The use of snowmobiles in the vast park north of Milville creates sun acceptable levels of air pollution and should be banned.

Milville business spokesperson: Snowmobiling brings many out-of-towners to Milville in winter months, to the great financial benefit of many local residents. So, economics dictate that we put up with the pollution.

Environmentalist: I disagree: A great many cross-country skiers are now kept from visiting Milville by the noise and pollution that snowmobiles generate.

Environmentalist responds to the business spokesperson by doing which of the following?

E. Denying that an effect that the spokesperson presents as having benefited a certain group of people actually benefited those people

Yes there seems to be a problem with the question. Your answer will actually depend on how you think. I chose E too. since the question is Environmentalist responds to BS by doing which of the following.....
the Environmentalist is actually denying that out of towner's are bringing any financial benefit to the residents of the state ( who probably have some business related to snow activities) and thus negating his reasoning.

I did think about A but the reason why i didn't choose it was--

Challenging an assumption that certain desirable outcome can derive from only one set of circumstances

I agree that this statement is true. however its not doing great to the entire conversation. Its like telling the BS that - Brother you are wrong. We have already banned those skiers due to noise pollution hence your assumption that skying is bring financial benefit is incorrect. however there can be other activities too which can in turn bring financial benefit.

But the point here is not financial benefit. The point that the Environmentalist raised was air pollution. by choosing E the environmentalist is negating the reasoning that BS has given. Which in turn strengthens the stand of environmentalist that we need to take steps to curb air pollution by banning snowmobiles.

lunarpower wrote: Ron is an Instructor and Manager of Curriculum Development at ManhattanGMAT. He takes pride in his inimitable sense of style, whether in his writing, in his clothes, or in his fascinating but useless talents.

Interesting ........

The source for this is GMAT paper-based tests.