answer: Diana cannot go to Hong Kong because she has a test and she asks Peter to go without her.
documents: #Person1#: Hey, Peter. I'm sorry.
  #Person2#: Hi, Diana. What's wrong?
  #Person1#: We were going to Hong Kong this weekend. But I'm afraid I can't go.
  #Person2#: How come?
  #Person1#: I have a really big geography test and I have to study for it.
  #Person2#: We can go next weekend instead?
  #Person1#: No, I don't want to ruin your weekend. You go ahead and please take the book I bought to my friend Sally. Tell her I have to study all weekend, because I can't afford to fail the test.
  #Person2#: OK, then I'll go with them. But it's a pity you can't come.