--Jack, is this your jacket?--No, it _______ be my jacket. My jacket is black but this one is blue.
--- Excuse me, could you tell me how ______ to Beijing Zoo? --- Well, you may take Bus No.27.
Where's Tom? His mother ______ him now.
Paul and I ______ tennis yesterday. He did much better than I.
I knocked on the door but ______ answered.
--- Can you ride a horse? --- No, I ______.