All the students know shouting at the elderly is impolite.
| A．can | B．could | C．must | D．need |
— Would you mind my taking this seat? — ______.
A.Sorry, I can’t B.No,not at all C.It’s a pleasure
— ____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