A、A more economical diesel fuel. B、Characteristics of a new type of fuel. C、Where a new energy source is located. D、How to devel

W: Hello? May I speak to Bill Johns?
M: Hi, Amy. This is Bill.
W: Oh, hi, Bill. You weren’t in engineering class today, were you?
M: No, I wasn’t. (20)I have a flu. I was wondering if you could tell me what went on.
W: I’m sorry that you are ill. Actually we had an interesting class. (19)Dr. Collin talked about a new type of fuel.
M: Oh, yeah? Tell me more about it.
W: Uh-hum. It’s called DME.
M: Oh, I remember reading something about DME. It’s mostly used in spray cans, right?
W: Right. DME doesn’t destroy the ozone, so it’s been environmentally friendly.
M: But doesn’t DME pollute the air if it’s burned in an engine?
W: Dr. Collin says something about its exhausts being clear, that it doesn’t release as much pollutants as diesel fuel. He mentioned something about DME being more efficient than other alternative fuels.
M: When will it replace diesel fuel?
W: Not for a while. It’s not economical to mass-produce. But it may happen in the future. After all, time will tell.
M: Well, thanks for the information. (21)I guess I won’t need to borrow your notes.
W: (21) Well, maybe you should look at them. We are having a test next week. You have to prepare for it.
M: Okay, could you give them to Mike Andrews? I think he is in your psychology class. He is my roommate.
W: Sure. I hope you’re feeling better soon.
M: Thanks. Me too. Bye!