Choice D is the best answer. The passage specifically states what Nawab considers the greatest part of his getting a new motorcycle: "Best of all, now he could spend every night with his wife" (lines 81-82,"further...his wife").
Choices A, B, and C are incorrect because the passage explicitly states that Nawab believes the best thing about his new motorcycle is that he can "spend every night with his wife," not that people start calling him "Uncle" (choice A), that he is able to expand his business (choice B), or that he is able to educate his daughters (choice C).