—Listen ! Helen is singing in the next room.

—It _______ be Helen. She has gone to Beijing.

A. can’t????? B. mustn’t????? C. may???? D. should??

---Listen! Helen is singing in the next room.

---It ______ be Helen. She has gone to Beijing.

1. A.
   can't
2. B.
   mustn't
3. C.
   may
4. D.
   should