A、Because he believes new kinds of machinery will be invented. B、Because he believes atomic power will be the only sort of power

W: What did you think of the lecture?
M: I thought it was very interesting.
W: Did you really?
M: Yes, didn’t you?
W: Certainly not. I thought he talked a lot of rubbish.
M: So you think you know more than he does.
W: Well, take coal for instance.
W: What about it?
M: Coal won’t become important again.
W: Why not?
M: It’s too dirty. They won’t be able to find people to work down in coal mines in the future.
W: They’ll invent new kinds of machinery.
M: Nonsense. The only sort of power they’ll use in the future is atomic power.