Look at the mess the boys made! You _______ have taught them how to behave themselves.

I _____ you somewhere before , but your name has escaped me _____ moment . 

--Where is Xiao Wang?--I don’t know. He__________ be in the library.

 Mr. Li, a man calling himself Smith wants to see you. ________ he come in?

According to the school rules, no student _____go out of the school after eleven o’clock at night without the teacher’s permission.