It is raining .
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.
--- Alice , you feed the bird today , ______? --- But I fed it yesterday .