— Look at the boy playing basketball on the ground. Is it George?— It ________ be him. He told me he would play basketball after class, but he’s not sure.

John, look at the time._____ you play the piano at such a late hour?

The boss ______ the worker how to do it, or the accident couldn’t have happened.

---Do you know why Anna hasn’t come to school today? ---I’m not sure. She _______ be ill.

I _____ have watched that movie --- it’ll give me horrible dreams.