—What's up? You look really down.—My wallet, mobile phone and ID card _______, I have called the police but I have heard nothing from them up to now.
—Must I turn off the gas after cooking ? —Of course . You can never be _______ careful with that.
_____ 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?