---What’s Mother doing, Jim?---I don’t know. She ________Zhou Libo’s show at her bedroom.
----______is the population of your city?-----About two million.
Please open a window _________ turning on air conditioning.
In those days ,books could only be produced one at a time _____________.
Food safety is important. Rules _____ to stop people from food pollution.
—Why don’t we start a school magazine on line? —________