______ of his time ______ been spent on studies every day.

We often go shopping _________ weekends.[ ]

The book ________ be Tom’s. Look! His name is on it.

Look at the glasses on the desk. Are they David’s?—They belong to him. I saw him go out with glasses just now.

Sally, could you go and help your father wash the car?—Why ____________? I’m busy now. Amy is lying on the grass doing nothing.