A、The problems of environment pollution. B、A material which can save fuel. C、The installation of pollution filters. D、The way to

W: Hi, Mike.
M: Hi. I’m surprised to see you on the city bus. Why not drive your car?
W: (23)I’ve been thinking about the environment lately. If we all use public transportation when we could, the air will be much cleaner.
M: Right. But the bus isn’t exactly pollution free.
W: True. But they’ll be running a lot cleaner soon, We were just talking about that in my environmental engineering class.
M: What’s the city going to do? Install pollution filters of some sort on their buses?
W: They could, but those filters make the engines work harder and really cut down on fuel efficiency. Instead they found a way to make their engines more efficient.
M: How?
W: Well, (24)there is a material called the coniine oxide. It’s a really good insulator. And a thick coat of it gets sprayed on the certain part of the engine.
M: An insulator?
W: Yes. (25)It reflects 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, right?
W: Yeah, and the bus will need less fuel. So with the savings on fuel cost, they say this will all pay for itself in just six months.
M: Sounds like people should all go out and get this stuff to spray their car engines.
W: Well, not really that easy.  To melt the materials before you can spray a coat of it on the engine parts, you first have to heat it over 10,000 degrees.  It’s not something we are able to do ourselves.