Listen! Is Mary singing in the next room?—No. It _______ be Mary.She has gone to Shanghai for an important meeting.
___ is believed ___ more and more people would fly to the moon in the future.
Are you _____ in these _____story books?
_____ there some milk in the bridge?- No. There ______ only two bottles of orange juice.
I have been trying my best to study English ________ I want to have a chance to be a volunteer for the Beijing Olympics. [ ]