Not until some students failed in the exam _____ how much time they had wasted.
| A．didn’t they realize | B．did they realize |
| C．they didn’t realize | D．they realize |
The reason for his success is ______ he worked very hard.
| A．that | B．why | C．whether | D．how |
Don’t try to cheat the taxman(税务人员); you’ll never ______it.
| A．get out of | B．get into | C．get along | D．get away with |
The chairman asked me to ______my speech to 20 minutes.
| A．make | B．give | C．limit | D．explain |
Seeing the enemy, Gary was behaving as though nothing ______.
| A．happened | B．had happened | C．would happen | D．was happening |
—Who______ it be that is knocking at the door?
—It ______ be Father, but I’m not sure.
| A．can; must | B．can; may | C．must; can | D．may; must |