【正确答案】 C

【答案解析】[听力原文]27-30 Man: My secretary tells me that you'd like to know something about mechanical engineering. What I can do is give you some idea of the variety of specialties within the field. Woman: I'd appreciate that very much. Man: One of the oldest mechanical engineering areas is machine design. First, we need to know the purpose, of a particular machine, whether it's a crane or a tool or a steam engine. Then, if we know the loads that this machine will carry, we can make the most efficient use of the materials we have. Woman: I see. Is heating included in this field? Man: Oh, yes. Heating, refrigeration, and air conditioning rely quite a lot on thermodynamics and theories of heat transfer. The goal is to make the most efficient use of power. This area can be quite involved with mathematics. Woman: I've heard of the Carnot cycle. Does this concern the mechanical engineer? Man: Very much so. The whole field of internal combustion engines is based on the principles set out by Carnot. The mechanical engineer deals with two and four-cycle engines, gasoline and diesel engines, gas turbines, and the like. Woman: Isn't that part of automotive engineering? Man: Yes. This is one of our largest industries. Woman: What about the aircraft industry? Man: Of course. Aeronautical engineering became a very large field with the widespread use of airplanes. Now, with space travel, it promises to grow even larger. Woman: Well, you've been most helpful, sir. Man: Not at all. Come in again. 27. Why has the woman come to the man's place?