If you _____ leave early on weekdays, do it quietly. The other classmates are also dying to have an early leave.

You ______ be polite to the old man.

Take care! Accidents _________ happen along this part of the road.

 When Marx was in London, he  __   read at the library for hours.

Holiday shopping ___be a tiring experience．There are so many places to visit and choices to make．