Assumption question

[rico16rad]

Sorry for posting this question in ManhattanGMAT verbal strategy guides .As I was not allowed to post this in general forum and as this argument was discussed in one of the Ron's session ,I preferred to post it here.


If a person chooses to walk rather than drive, there is one less vehicle emitting pollution into the air than there would be otherwise. Therefore if people would walk whenever it is feasible for them to do so, then pollution will be greatly reduced.

Which one of the following is an assumption on which the argument depends?

A) Cutting down on pollution can be achieved in a variety of ways.
B) Taking public transportation rather than driving is not always feasible.
C) Walking is the only feasible alternative to driving that results in a reduction in pollution.
D) There are people who never drive but who often walk.
E) People sometimes drive when it is feasible to walk instead.



Hi Ron,
How are you? Hope you are doing good. While going through the video session of 4 th March 2010 ,I came across this question ,the question mentioned above.I am little confused about answer choice C.Though this is very strong,I don't find exact reason to remove this.As per my understanding this is a Casual reasoning argument asking for Assumption.
So there can be two important part which we must look into and those are :
1. We must consider the answer choice, which says that there is no other cause for same effect.

Answer C does say that only walking can help to decrease the pollution ....Still why is it wrong.

2. To see the reverse is not possible mean the decrease in pollution doesn't cause people to prefer walking over driving.
Please explain me this.Please let me know if I am wrong in my points, which I have clarified above.

Thanks,

[tim]

The proper approach here is to negate answer choice C. Ask yourself what would happen if the opposite of C were true. If that would destroy the original argument, then C is a necessary assumption. If there is any way the argument can stand despite C being negated, then C is not a necessary assumption..

In this case, C says walking is the ONLY alternative that reduces pollution. If we negate this, we say that there are other pollution-reducing alternatives besides walking. If there are other such alternatives, does that completely destroy the author's argument that walking when feasible will reduce pollution? Not at all. Thus C is NOT a necessary assumption..

What is the source for this problem BTW?

[JbhB682]

Sorry for posting this question in ManhattanGMAT verbal strategy guides .As I was not allowed to post this in general forum and as this argument was discussed in one of the Ron's session ,I preferred to post it here.


If a person chooses to walk rather than drive, there is one less vehicle emitting pollution into the air than there would be otherwise. Therefore if people would walk whenever it is feasible for them to do so, then pollution will be greatly reduced.

Which one of the following is an assumption on which the argument depends?

A) Cutting down on pollution can be achieved in a variety of ways.
B) Taking public transportation rather than driving is not always feasible.
C) Walking is the only feasible alternative to driving that results in a reduction in pollution.
D) There are people who never drive but who often walk.
E) People sometimes drive when it is feasible to walk instead.



Thanks,

I agree A/B/C and D are not the best but i thought E has an issue too

Negating option E (which is the OA) is the following :

people never drive when its feasible to walk instead

Doesn't this go against the if statement in the premise in blue ?

Negating E seems to go against the premise of the question completely ...My understanding was the accurate assumption does not go against the premise in the question

[Sage Pearce-Higgins]

You're right that when we apply the negation test the correct answer (the actual assumption) will make the argument collapse and that we can't go against a fact stated in the argument. However, the blue part shows an interesting point about 'if...' clauses in premises. When we see and 'if...' clause, we can't assume that the part after 'if' will definitely happen. Sure, we can accept that if people did drive less, then there'd be less pollution while challenging the possibility: what if it's not possible for people to drive less? This is what answer E does.