F: Tom, why are you surfing the net again? It's a real waste of time I've told you.
(A) M: Although you think it can save time, I don't know how to surf the Net. (B) M: Surfing the Net is not a waste of time. And I have never surfed the Net before. (C) M: Mom, it is not a waste of time. I can use the Net to do a lot of things. (D) M: Just a minute! I do not quite follow what you are saying, would you mind repeating that?
C