—How is your grandma?—She’s fine.She used to________TV at home after supper.But now she is used to________out for a walk.
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? —________
The sign means _________