If Skiffs book is published this year, Professor Nguyen

Take a look at the exact wording of the answer choice:

So, we need an assumption that, combined with the evidence from the passage, allows us to properly infer the conclusion. Note: you will not see this form of question on the GMAT (where assumption questions will be some form of "the argument depends on which assumption?") Proceed only if this question has piqued your curiosity, otherwise your time is better spent on questions that align more closely to the GMAT.

Let's break down the passage to see where that assumption needs to fit in:

• Fact 1: If Skiff's book is published this year, Prof. Nguyen will urge the dean to promote Skiff.
• Fact 2: Prof. Nguyen will keep her promise, and the dean will promote Skiff if Nguyen recommends it
• INSERT ASSUMPTION HERE
• Condition on the conclusion: If Skiff's book is as important and well written as he claims,
• Conclusion: Skiff will be promoted.

We are looking for an answer choice that, when inserted in the passage as described above, allows us to infer that the conclusion follows.

Let's first look at (D):

This tells us ONE reason why Skiff's book will not be published, but it does not tell us that it is the ONLY reason that his book may not be published. An infinite amount of other things could happen to prevent Skiff from publishing his book -- maybe his manuscript will be burnt to a crisp in a housefire, or maybe he'll decide to leave academia and take up subsistence farming on some remote island.

If one of these other scenarios occurs, then Skiff STILL will not be promoted, even if we assume the truth of (D). So, (D) does not GUARANTEE that the conclusion follows logically from the evidence in the passage. For this reason, (D) is out.

Compare that to (A):

Remember, Professor Nguyen doesn't care whether Skiff's book is important and well written -- If it is published this year, she will urge the dean to promote Skiff, and the dean will promote him. To get this chain of events to occur, we just need to prove that Skiff's book will be published.

(A) tells us that the book will be published if it is "as important as he claims it is." So, if it reaches that bar, the following will occur: the book will be published, Nguyen will pester the dean, and Skiff will be promoted.

The passage adds another criterion on to this list: Skiff will get promoted if the book is not only important, but also well written.

But remember, Nguyen doesn't care about these factors! If we assume (A), then we KNOW that if the book is important it will be published, and the rest of the chain of events will occur. This is a LOWER bar than assuming that the book is both important and well written. So, if Skiff will be promoted NO MATTER WHAT if he writes an important book, then he will certainly be promoted if the book is both important AND well written.

In other words, (A) fills in the gap between the evidence and conclusion in the passage -- if (A) is assumed, then the conclusion follows. The same can not be said for (D) -- if (D) is assumed, the conclusion might follow, but it also might not.

(A) is the correct answer.

I hope that helps!