答案：解析：

A: Which do you think is the most useful invention?

B: I think the most useful invention is the light bulb.

A: Why do you think so?

B: Because it gives people more time to work and play every day. What about you?

A: I think the most useful invention is the telephone.

B: Why is that?

A: You can talk to your friends far away with it. What would you most like to invent?

B: I'd like to invent a pen that I can write faster, but as neatly as the usual one. What about you?

A: I'd like to invent a car. When I am in the classroom, I can put it in my pocket.

B: That's sounds interesting. We must work hard if we want to make our dream come true.

A: You are quite right. Let's work hard together.