She is a quiet girl at school，but sometimes she _____ be very naughty.

 – Excuse me, sir. But nobody _____ smoke here in the lift! -- Sorry! I didn’t see the sign. 

—Look at the picture on the wall. It ________be David’s.—Yes, his name is on the first page.

I got close enough to hear them speaking Chinese, and I said “Ni Hao ” just as I ____ do in China.

— Li Lin hasn’t turned up yet, but he promised to come to the party.— He ______ home. He is a man of keeping his word.