—Be quiet, Mr. Smith is coming.—Don’t worry. It ___ be him. Mr. Smith is much taller.A. mustn’t B. must C. can’t
Some of my friends are interested in science, but none of them can tell ________.
______ your English teacher ______ you ?
They were talking about the persons and things _______ they saw in the factory.
Not only the students but also their teacher_______ the Great Wall before.
It is impossible for ______ little children to do ______ much work within 20 minutes.