a．I found that the factory was pouring waste water into the river a few days ago.

　　b．Have you ever seen him before?

　　c．Where have you been?

　　d．I've written a report about it．

　　e．The paper factory has been built for 3 years．

　　f．I've been to a paper factory．

　　g．Maybe he's gone to a paper factory．

　　A：Where's Li Hua? Do you know?

　　B：1

　　A：What did he do then?

　　B：I don't know．He'll be back in an hour．(After an hour)

　　A：Li Hua，2 ndline　 I called you an hour ago，but you weren't in your office．

　　C：3

　　A：What did you do there?

　　C 4 ndline　 The river has become very dirty．Lots of fish have died．

　　A：That's terrible!

　　C：Do you think“Greener China”can do something?

　　A：Yes，of course．We can write a report about it to the TV station and the newspaper．

　　C：You're right．5 ndline　 Can you read it?

　　A：Great! Let me read it．

— I think the man over there must be Bob.

— It _______ be him. He has gone to England.

A. can’t          B. mustn’t        C. couldn’t            D. shouldn’t

-There is someone knocking at the door.

- It ______ be Jimmy, he has gone to ShangHai .

A．needn’t         B．mustn’t          C．can’t            D．may not