---John, my computer doesn’t work. --- Why not ask Mr. Liu __________ it?A. checking B. to check C. to buy
—Why do you look so tired? —Because we ________ for three hours without stopping.
We won’t start the meeting ________ the teacher arrives.
The workers are trying to ________ what’s wrong with the machine.
Internet is ________ used by people, especially by young people.
It’s so fine. Why not ________ outdoors?