If you know nothing about the famous program called Where are we going, dad?, you ______be living in a box!

—Listen! There is a knock on the door. Who _____ it be?—It must be Jack. Just now I sent for him.

That man in the corner of the restaurant ______ be Mr. Lee, for he went to Australia yesterday.

—Can I pay the bill by check?     —Sorry, sir. But it is the management rules of hotel that payment _____ be made in cash.

—Look at the picture on the wall. It ________be David’s.—Yes, his name is on the first page.