I'm sorry I haven't, Mrs. Smith. I've already finished the exercises, but I can't find my exercise book anywhere now.
Really? I don't understand why you are always forgetting to hand in your exercise book. You are lying.
Mrs. Smith, I'm not lying this time.
I'm really angry with you. If you don't tell me the truth, I'll have to call your parents after class.
I'm sorry my parents have gone to Beijing. They'll be back in half a month.
I don't believe you. It was yesterday that I saw your parents in the supermarket. You're very clever, but you never spend your time doing your math exercises. Sit down, please. Let's get down to business.