Choice D is the best answer. The previous question asks why the narrator considers Great Expectations to be the greatest gift he ever received. The answer, that the book convinced him to become a writer, is best supported by the last sentence of the last paragraph: "Soon I was convinced that I didn't want to do anything else in life but learn to do what Mr. Dickens had done."
Choices A, B, and C are incorrect because the cited lines don't support the answer to the previous question. Instead, they explain the narrator's interactions with the bookseller (choice A), describe the book's physical condition (choice B), and indicate the narrator's initial, erroneous assumption that Sempere knew Charles Dickens personally (choice C).