punitkaur wrote:Proponents of the electric car maintain that when the
technical problems associated with its battery design
are solved, such cars will be widely used and, because
they are emission-free, will result in an abatement of
the environmental degradation caused by auto
emissions. But unless we dam more rivers, the
electricity to charge these batteries will come from
nuclear or coal-fired power plants. Each of these three
power sources produces considerable environmental
damage. Thus, the electric car _______.
Which one of the following most logically completes
the argument?
(A) will have worse environmental consequences
than its proponents may believe
(B) will probably remain less popular than other
types of cars
(C) requires that purely technical problems be
solved before it can succeed
(D) will increase the total level of emissions rather
than reduce it
(E) will not produce a net reduction in
environmental degradation

The correct answer must be choice A.

The first sentence gives us the POV of the "proponents". They think that the electric car will "result in an abatement of the environmental degradation caused by auto emissions". Their argument can be summed up as: "electric car will lead to less auto-emission-induced env dmg".

The next sentence (ie, second sentence) begins with the contrast keyword "but". This tells us the author is out to argue against the proponents--so, at this point, we know he will generally argue that electric cars are actually not a cure-all. This sentence and the next one (third one) must be evidence because the fourth sentence (the one we have to complete) begins with "thus".

To complete the author's POV correctly, we should examine his evidence. Well, the third sentence ain't so bad as it just tells us that the electricity that will run these electric cars comes from nuclear or coal-power sources. The fourth sentence tells us that each of these sources "produces considerable environmental damage".

But notice the author's evidence (considerable environmental damage) does not establish whether, overall, a switch would mean more environmental damage. He never compares levlels of environmental damage. So choice E is wrong, and choice D is extreme, and wrong for pretty much the same reason. The author's main point , then, is that electric cars are not the cure-all their proponents think them to be--that there will still be considerable environmental damage even if we switch to them.

The author's POV, then, can be summed up as: "because the production processes for these electric cars are environmentally damaging, switching to electric cars won't necessarily reduce environmental damage".
Choice A is a perfect match to this prediction; choose A.

In inference questions (complete the blank questions are just inference questions), the passage and the correct answer are always things that must be true. Therefore, the wrong answers are things that could or must be false. Therefore, you can use denial test: If the author did not believe in choice A, would his argument make any sense? Would his argument still be available to him?

Well, here, if the author did not believe in choice A--if he believed its' opposite--it would mean that he thought the proponents are bang-on in their optimistic prediction about electric cars. Then, what the heck explains the "but"? If the author did not believe in choice A, then his statements do not make any sense at all. More technically, if choice A were false, the passage would be falsified, but, in inference questions, we must always treat the passage as necessarily true. Therefore, he must believe in choice A: it must be true.

Choice E looks like the "trap" answer here. Let's try denying it. When you see "not", just deny by removing "not". So, if the author thought that a switch would produce a reduction in env dmg, do his statements still make at least some sense? Is his argument still available to him? Yes, his statements surely still make at least some sense because he said nuclear and coal power is environmentally damaging; he never compared the specific level of env dmg from nuclear/coal power to current cars. More technically, if choice E were false, the passage is not necessarily falsified. Therefore, choice E is not necessarily true: it could be false.

In inference questions, focus on the connections between sentences, and (especially in the complete-the-blank variety), try to think about what the author's main point is, what he is trying to get at.