---There’s someone knocking on the door. Who _________ it be?---It must be John. He promised to be here at 8:00.

I am fond of my sister but she has one serious shortcoming. She _________ be really stubborn.

I ______ worry about my weekend—I always have my plans ready before it comes.

—He should have come to join in the thorough cleaning.—He _____. I don’t think it was his turn.

 --Tibet, a part of China can not suddenly become its own country.--_______. All the Chinese people are against it