______ I have a quick word with you? Something important has happened.

—Listen ! Helen is singing in the next room.—It _______ be Helen. She has gone to Beijing.

My sister met him at the Grand Theater yesterday afternoon, so he ________ your lecture.

—Who’s that over there, Is it Jane?—No, It ________ be Jane. She is ill in hospital today.

The boy is old enough to ---------himself.