You ______ be hungry already—you had lunch only two hours ago!

Students ___________ remain in their seats until all the papers have been collected.

If prices rise too high, the government has to do something _________ it. 

In China, you _____ vote when you are 18.

-----Look! The girl dancing in the gym ____ be Joe. She is the girl who loves dancing too much, you know. ----- No, it ____ be her. Joe has gone to Shanghai.