— ____can we board our plane? — In twenty minutes.
A.How soon B.How long C.How often
My e-mail______to you last night. Have you received it____?
A.sent;yet B.is sent;already C.was sent;yet
Several days has passed_______the air crash（空难） happened.
A.since B.after C.as
In our school libray,there____a number of books on science and the number of them_____growing larger and larger.
A.is;are B.are;is C.have;is
They preferred_____ rather than_____a bike.
A.to walk; to ride B.walking;riding C.to walk;ride
You______be tired after playing sports for a long time without a rest.
A.must B.need C.can’t
