answer: Li tells Bobby that Li's stuck in the traffic jam and will be late for dinner. Bobby will put off the dinner till one o'clock.
documents: #Person1#: Hello, Bobby, It seems that I can't arrive at your home by 12 o'clock.
  #Person2#: What happened? We're all expecting you, Hans, Dick, Archie. . .
  #Person1#: I'm so sorry, I've been held up by the damn traffic jam for half an hour. I'd have arrived but for that.
  #Person2#: I see. Where are you now, Li?
  #Person1#: Thirty meters ahead is the Waterloo Bridge.
  #Person2#: It's not far away from home, It's - let me see, about 20 minutes'walk, Can you walk here?
  #Person1#: I've thought of that, but what can I do with my car? If only I had taken a taxi!
  #Person2#: That's too bad, But don't worry. We'll put off dinner till one o'clock.
  #Person1#: I'm so terribly sorry to keep you waiting.
  #Person2#: It doesn't matter. Bye.
  #Person1#: Bye.