Last time this writer wrote a book, it sold quite well because she worked in collaboration with another writer. Therefore she should collaborate with another writer on her next book so it will sell well.
One interesting way of looking at this one is to notice how conditional logic, causation, and comparison all move together in a rare show of unison. The argument definitely possesses a causal structure (collaboration caused her last book to sell well). It also contains a bit of comparison, comparing the success of her last book with that of her next book.
But on Principle questions, it's conditional logic that generally rules the day. And this one is no exception. Since we want to support the argument with a principle, we want to connect the evidence with the conclusion, which answer choice (C) does quite nicely.
Incorrect Answers
(A) might be tempting at first glance and is one that I'd likely hold onto until a second round of eliminating answers (just in case there is nothing better), but it stipulates working with the same collaborator, while the argument does not.
(B) reverses the logic.
(D) fails to connect the evidence.
(E) fails to connect the evidence.
#officialexplanation