M: Talking about the twenty first century, I think there will be huge changes in the way people use cars. Laws will be made about what kind of car you can own, and when you can use it. ,F: Maybe there'll just be too many of them on the roads. The air will be so seriously polluted that nobody will be able to breathe normally. ,M: Exactly, people will have to rely on trains. ,F: Why do you say that? ,M: Well, we won't be able to use cars and the airports take too much space. That leaves trains.
(A) F: Yeah, the air will be so seriously polluted but we will be able to breathe normally. Oh, let's continue to talk about the air pollution. (B) F: So, you mean the airports take too much space but that doesn't leave trains? Okay, I see. Let's continue to talk about the transportation. (C) F: Just a minute! I do not quite follow what you are saying, would you mind repeating that? (D) F: So, you mean we won't be able to use trains and the airports take too much space? Okay. Let's continue to talk about the road connection.
C