---David,is that man your Chinese teacher?---It___________ be him.He’s having a meeting.
Anna is _____ to work out the math problems and gets a good grade.
Who listens _____,Tom, Jack, or Bill?
_____ it is raining, _____ he is still working outside.
--_____ did you ________the summer vacation? -- It was terrible . I have too much homework to do .
Mary tries ____ vegetables eleven or twelve times a week because she wants to be ____.