--Who______ it be that is knocking at the door?
--It ______ be Father, but I’m not sure.
| A．can; may | B．can; must |
| C．must; can | D．may; must |
--- Why were you absent yesterday?
--- I caught a cold, _______I had been walking around in the rain.
| A．but | B．so | C．and | D．for |
A subway is an effective way to solve traffic problems in_________big city. It has evident advantages, such as_______speed and convenience.
| A．the; the | B．a; the | C．a; / | D．the; a |
It’s the ability to do the job _______ matters not where you come from or who you are.
| A．one | B．that | C．what | D．it |
Would you do me a(n) _______ and open the window? It is so hot in the room.
| A．help | B．favor | C．aid | D．service |
I am going to the post office. Do you have any letter _________?
| A．to be sent | B．to send | C．sending | D．sent |