1. 选词填空

must, should, ought(nt)to, don't, have to, couldn't, mustn't, needn't, have to

1. （1） You go on working because you look so tired now.
3. （2） Li Hua pass an examination before he can start work.
5. （3） You come to the meeting if you're too busy.
7. （4） You play now! You shall finish your homework first!
9. （5） I know things are hard with you, but you try to get over the difficulties.
11. （6） I didn't see her at the meeting this morning; she have spoken at the meeting.
13. （7） You imagine what difficulty we had walking home in the snowstorm.
15. （8） The weather turned out to be fine yesterday. I have taken the trouble to carry my umbrella with me.
17. （9） You follow the doctor's advice. I think it will do good to you.
19. （10） I have phoned Ed this morning，but I forgot.