---Who is the tallest boy? ---It ______ be John.. John is of medium height.
—May I watch TV, Mom? —I’m afraid you _______.
We don’t know how to prevent the flu. Shall we ask Doctor Wang Hai for______?
—Humans can’t live _______ air. —I agree with you.
—Who taught _______ Japanese? —I learned it by _______.
—You’d better not read _______. It’s bad for your eyes. —You’re right. I won’t do that again.