Unless ___ to speak,you should remain silent at the conference.
You are students in the No.168 Senior High School now, but you _______ in different junior high schools for three years.
Being injured in the leg made _______ impossible for him to walk his way home.
It is believed that a new kind of drug _____ by the scientists and they are hopeful that they will succeed in a few months.
— He was given a free five-day trip to Hainan.— He _____ it since he has worked so hard.
—When was Tom bitten by a snake?—It was on a Sunday _______ he was taking a trip to the mountainous area.