OG6 阅读 Q3

Choice D is the best answer. The passage states that Nawab works "like an engineer tending the boilers on a foundering steamer in an Atlantic gale" (lines 26-28,"heaters...gale") in his attempts to keep his employer comfortable. The author likely uses this image because it highlights the challenging nature of Nawab's work—work that is described in the next sentence as requiring "superhuman efforts" (line 28,"in...he"). 
Choices A, B, and C are incorrect because the author's use of the image of an engineer working hard on a "foundering steamer" describes the effort Nawab is making in keeping his employer comfortable, not what Nawab might be dreaming about, anything to do with tube wells (which are not mentioned in the second paragraph), or that Nawab has had many different jobs in his life.