---There is somebody knocking at the door. Who________ it be?---I’m not sure. It ________ be a postman.

— I heard they went skiing in the mountains last winter. — It ________ true because there was little snow there.

--- Look, Mr Green is on the other side of the street. --- It _____ be him.He has gone to London on business.

You       buy a gift, but you can if you want to.

---Who is the tallest boy?      ---It ______ be John.. John is of medium height.