—What happened to the postman? —I don't know. He______ around here for a long time.
—How’s your tour around the North Lake? Is it beautiful? —It ________ be, but it is now heavily polluted.
John promised his doctor he _____ not smoke and he has never smoked ever since.
According to the air traffic rules, you ___ switch off your mobile phone before boarding.
When I was young, I was told that I ______ play with matches
-What sort of house do you want to have? Something big? --Well, it ______ be big--that's not important.