answer: Miss Smith is angry because Jack says he finished the exercise but can't find it.
documents: #Person1#: Have you handed in your exercise book, Jack?
  #Person2#: I'm sorry, I haven't, Miss Smith. I have already finished the exercise, but I can't find my exercise book anywhere now.
  #Person1#: Really? I don't understand why you are always forgetting to hand in your exercise book. You are lying.
  #Person2#: Miss Smith, but it is true this time.
  #Person1#: I'm really angry with you. If you won't tell me the truth, I'll have to ring up your parents after class.