— I telephoned him twice and I couldn’t get through to him.—I think that the line might have been out of order, _______?
_____ is known to everybody, the moon travels round the earth once every month.
It is so difficult a problem that _____ student in this class _____ work it out.
Shirley _____ a book about China last year, but I don't know whether she has finished it.
Who did the teacher have ___ an article for the wall newspaper just now?
Use an umbrella to _____ you from the rain.