At times, it’s good to step away from the argument and think about what is really going on and what the author is trying to say.
The negation test is a fantastic way to get you to think in these terms, but mistakes made when creating the negated form of the answer choice can lead to picking the wrong choice.
Basically, the author is saying we can reduce pollution by having people follow this course of action. If people choose to walk rather than choose to drive, we will reduce the pollution.
How does the author think this will happen?
The author uses the fact that whenever a person chooses to walk instead of drive, there is one fewer car on the road creating pollution. Therefore, if we get people to walk whenever it is possible for them to do so (instead of driving), then we will have reduced pollution.
There is always a “jump” made by the author from the facts to the conclusion.
In order for this explicit fact to support the claim that pollution will be reduced, it must be true (in the author’s mind) that cars will be removed from the road when ppl choose to walk.
The only way the claim is supported by the facts is if cars (which emit pollution) are actually removed from the road when people choose to walk.
-C- “Walking is the only feasible alternative to driving that results in a reduction in pollution.”
To get from the facts to the conclusion, is the author required to believe that walking is the ONLY feasible alternative that results in a reduction in pollution?
When a person says if we do this one thing X, then this other thing Y can happen, she’s not worried about whether there are other things that can lead to Y occurring. The focus is just on whether doing X can get Y to happen.
Similarly, in this argument, the author is making the claim that if people choose to walk, there will be a reduction in pollution. She believes choosing to walk instead of drive is one way to get to that reduction. If there are other feasible alternatives to walking, this fact does not impact whether choosing to walk will lead to the reduction.
There could be dozens of alternatives and the author’s claim could still be correct. It wouldn’t matter. When people choose to walk instead of drive, a car is removed. And if enough of these cars are removed, the reduction in pollution can still occur.
Thus C is not a REQUIRED assumption.
-E- “People sometimes drive when it is feasible to walk instead.”
In order to get from the fact of ppl choosing to walk instead of drive to the conclusion that pollution will be reduced, it is required that cars come off the road when ppl choose to walk. After all, this is the mechanism that the author believes will result in less pollution. She believes that each time a person chooses to walk, there is one car removed from the road.
In order for the premise to support the conclusion, it has to be the case that some ppl actually drive when they could feasibly walk instead. Otherwise, there would be no one driving a car on the road right now who could feasibly choose to walk.....and no ADDITIONAL cars would be taken off the road by following the author’s suggestion.
In such a case, all the people who could feasibly choose to walk are already not driving. There are no other cars that can be taken off the road, thereby reducing pollution.
Therefore, the author must assume that there are people who sometimes drive when it is possible for them to walk instead.
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