This question asks us to find the conclusion of the argument. The first sentence is background information. The second sentence can be broken into two parts. The part before the semicolon is the conclusion of the argument and everything after the semicolon is the evidence for why the publisher’s conclusion is true. This is something that is typical of an Identify the Conclusion question.
_______ : ___________ .
Conclusion Evidence
So the conclusion should be something along the lines that "we must do whatever it takes to ship the books on exercise and fitness on time." This is best stated in answer choice (D).
(A) is not quite right. The conclusion is about shipping books in the exercise and fitness category, not books in general.
(B) is not even necessarily true.
(C) is also not even necessarily true.
(D) restates the conclusion perfectly.
(E) is not true. The publisher just thinks they have to do a good job. They don’t have to adopt their competitors’ strategies.