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

We can eat in the dining hall. But we _______ eat in the classroom.

---Listen! Is Kate playing the piano in the room? ---No. It _________ be her. She has gone to London with her parents.

—Look! Is that Mr. Green?—It          be Mr. Green. He has gone to Shanghai.

— Must we get to the theater at 7:00?— No, you _______. The movie begins at 8:00.