20．The doorbell rang，and mother _______ the door．

A．stopped open B．stopped opening

C．stopped to open D．stopped opened

19．Do you know _____ this time yesterday?

A．what they are doing B．what are they doing

C．what they were doing D．what were they doing

18．Li Yong ______ sweep the floor this morning．

A．was seen to B．was seen C．saw D．saw to

17．Please buy some stamps for me if you _____the post office.

A．pass B．will pass C. have passed D. passed

16．一______ I copy all the new words in this lesson?

一No，you ______. You copy some of them．

A．Can，can't，can B. May，mustn't，may

C．Must，mustn't，can D. Must，needn't，may

15．We did ____ Mr Hu told us and we won the first place in the league at last．

A．though B．1ike C．as D．while

14．The twins lived there _________the years 1993-1995．

A．during B．between C．in D. at