—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
Elizabeth _______ a good plan of increasing sales at the meeting.
The woman ________ Mr. Brown is a professor from Beijing University.
The head teacher comes to the classroom ______ to see if the students are quiet.
I’ve been playing the piano for four hours and I am ________ it.
Look, a demonstration ________ on Main Street.