—Must I buy lunch at school?—No, you needn’t. You __________ bring your own lunch if you want to.

One of my friends _______ moved to America. I miss her so much.

---I don’t care what my parents think. ---Well, you __________.

The room is in a terrible mess; it        have been cleaned.

 —Look at the boy running on the ground. Is it David?—It      be him. I saw him go to the teacher’s office just now.