—Is Mr. Smith over there?—It ________ be him. He has gone to Beijing on business.
Food safety is important. Rules must ________ stop people from food pollution.
Our headmaster isn’t in his office. I can’t find him anywhere. Did you notice him ______ the office?
You must keep your eyes _____, let’s begin the game.
Thanks for ________ the secret ________ me.
When we practice speaking English, we often end up ______in Chinese.