—Which sweater can you choose, the blue one or the red one?—____ is OK, I think. Both go well with my trousers.
----______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? —________