--______ you leave now?
---Yes, because I’m meeting my aunt at 7:00 this evening.

—Mr. Wang, must I come again to clean the window on Sunday morning?
—No, you _____ . I have asked others to do it.

—How about singing songs with me?
—I’m sorry I can’t. I           help my father with his work.
A. have to             B. can                 C. may

---Must I hand in my exercise book now, Mr. Zhao?
---No, you ______. You may give it to me tomorrow.

—Must I go there right now, mum?
—No, you ____. You can go there tomorrow.

The police still haven’t found her, but they’re doing all they      .

—Look! The man at the gate ______ be our headmaster. He is always standing there every morning.
—No, it ______be him. He is holding a meeting in the office now.

---Must I work out the problem right now?
---Yes, you _______. It’s very serious.

—Bill, can I use your dictionary? I left mine at home.
—Of course you________. Glad to help you.

— Must we get to the airport before 8 o’clock?
— No, you _____. The plane takes off at 12 o’clock.