I’m in agreement with the previous person. Your answer would be D) Prolific.
Step-by-step explanation:
A. While the word fastidious does have mentions of the word fast in it, this option is meant more to throw you off. It means, to be very attentive to and concerned about accuracy and detail. While this could be true, this is not the focus of the sentence.
B. This answer can be eliminated right off the bat. Being about to create and publish that many books in the given amount of years exudes nothing, but confidence in one’s ability to produce work.
C. The incredible pace this author has worked at speaks nothing of being outmoded. When you think of something as being old-fashioned, your mind will most likely think of slow and behind the times. This is certainly not the case here.
D. As the previous person stated, the meaning of prolific is to present in large numbers or quantities; plentiful. This is exactly what was done here and can be applied perfectly in the given scenario.
E. This answer is completely irrelevant.