The boy often tries his best ___________ his parents happy.

_____ twenty years’ time , maybe there won’t be any school!

Must I do the rest of the work today— No. You _________finish ittomorrow.

It is easy to learn English well, isn’t it–_____. You should spend much time on it.

Listen! Kathy is playing the piano in the next room.—It __________ not be Kathy. She has gone to Hangzhou to visit the Cross-sea Bridge.