Now you'll hear the two long conversations.
Conversation One
M: Hi, Diana. I'm surprised to see you on the city bus. Your car in the shop?
W: No. [19]I've just been thinking a lot about the environment lately. So I decided the air will be a lot cleaner if we all use public transport when we could.
M: I'm sure you are right. The diesel bus isn't exactly pollution free.
W: True. They'll be running a lot cleaner soon. [20]We were just talking about that in my environmental engineering class.
M: What could the city do? Install pollution filters in all their buses?
W: They could, but those filters make the engines work harder and really cut down on the fuel efficiency. Instead, they found a way to make their engines more efficient.
M: How?
W: Well, there is a new insulator. And you spray a thick coat of it on the engine.
M: An insulator?
W: Yeah. [21]What it does is reflect back the heat of burning fuel. So the fuel will burn much hotter and burn up more completely.
M: So a lot less unburned fuel comes out to pollute the air. W: And the bus will need less fuel. So with the saving on fuel cost, they say this will all pay for itself in just six months.

Questions 19 to 22 are based on the conversation you have just heard.
19. Why does Diana take a bus that day?
正确答案：A
解析：男士问Diana为什么乘坐公共汽车，是不是她的汽车在维修。女士回答说不是，她乘坐公共汽车是因为最近她在考虑环境问题。大家都使用公共交通的话，空气会干净一些。可见她关注环境，故A正确。B未提及，C、D内容与对话不符。
20. What is true about Diana?
正确答案：C
解析：女士说到：“在环境工程课上我们刚刚谈到过这一点。”可见她修了一门环境工程课，故C正确。四个选项都以Diana为主语，本题定然问她的情况。要根据选项关键词听对话，把涉及关键词的信息与选项对照，判断选项正误。
21. What justifies the installation of a new insulator in the buses according to Diana?
正确答案：A
解析：对于安装新的绝热器，女士说：“它的作用在于它可以把燃料燃烧的热量反射回来，这样燃料燃烧时的温度就会更高，燃烧也就更彻底。”可见绝热器可以提高燃烧率，A正确。鉴于我们并不知道it指什么，听录音时，必须对有关事物予以重视。对话中，男士重复反问了一个词“An insulator?”表明它是对话中讨论的一个重点，问题it可能与它有关。紧接着女士的回答又用了“What it does is...”的强调结构，并用“So...”说明结果，相关内容即构成本题答案。
22. What is the major concern of the woman?
正确答案：D
解析：对话中女士有车不开，宁愿挤公交车；上环境工程课；对节能环保绝热器感兴趣，均表明她关注环境，有浓厚的环保意识。因此，D正确。实际上本题是问对话主题，选项D概括性最强，是答案。其余选项均是细节，或与对话无关。