(B) is the correct answer, and there is in fact no uncertainty about it. I’ll try to explain why.
First of all, it is really important to realize that for most assumption questions (not all), there are many assumptions, not one. That is, there are many different additional pieces of information that are needed in order to really prove the conclusion, but that were left out of the argument. This question is definitely of that type. Here are a few of the things that are not mentioned, but that have to be true (that is, the assumptions) in order to prove the conclusion:
- American paper manufacturers won’t buy so much of the American wood pulp that there is not much left for export.
- Japanese and European manufacturers are not ALREADY buying as much American wood pulp as the US can export.
- There is no characteristic or limitation of American wood pulp that would prevent Japanese and European manufacturers from using it, even though it would cost them less if they did. (Note that answer choice (B) is part of this one.)
In this kind of assumption question, the correct answer is one of the things that NEEDS to be true in order to prove the conclusion - but this answer is not ENOUGH BY ITSELF to prove the conclusion. In LSAT language, the correct answer is necessary in order for the conclusion to be true, but not sufficient.
So although it is true that (B) does not prove the conclusion, that doesn’t make it the wrong answer. (B) does have to be true in order to allow the conclusion to be even possible, and that makes it a necessary assumption, and therefore the right answer. Because we are looking for a necessary assumption, the “denial test” works for this question, as several people have already pointed out. The denial test works by contradicting the answer choice, and then seeing whether the CONTRADICTED version makes the conclusion impossible. If the contradicted answer choice makes the conclusion impossible, then the UNcontradicted answer choice must have been necessary in order to allow the conclusion. Thus, the uncontradicted answer choice must have been a necessary assumption.
The other choices are not necessary in order to allow the conclusion to be true:
A: They do not have to produce more paper in order to make American pulp exports go up. They could produce the same amount, but buy a lot more American pulp and a lot less of other countries’ pulp to do it.
C: They don’t have to prefer American pulp at an EQUAL price (or ignoring price) in order to make American pulp exports go up. We know from the evidence that American pulp will be really cheap. In order to make the exports go up, they only need to be willing to buy it AT THIS REALLY CHEAP PRICE.
D: I don’t think this one fooled anybody. It would be a reason NOT to buy more pulp from anyone, American or otherwise.
E: Production of American wood pulp does NOT have to stay at its present level in order to make exports go up. In fact, if the US is not able to increase its production of wood pulp, that might PREVENT wood pulp exports from going up. This one (like choice D) actually hurts the argument rather than helping it. The moral of this story is – every time you see the word “not”, make sure you know which way the statement is going.
Kaplan Canada LSAT/GMAT/GRE teacher and tutor