Nowadays, more and more people are using private cars, ________ has caused a lot of traffic problems, especially in large cites like Beijing and Shanghai.
| A. that | B.which | C.it | D.they | 
If I hadn’t been lucky enough to meet you. I really _____ what I would have done.
| A.don’t know | B.hadn’t known | 
| C.wasn’t knowing | D.wouldn’t know | 
“I still haven’t thanked Aunt Lucy for her present.” “It’s time you _____.”
| A.do | B.did | 
| C.had | D.would | 
— Lucy doesn’t mind lending you her dictionary. 
 — She _______. I’ve already borrowed one.
| A.can’t | B.mustn’t | C.needn’t | D.shouldn’t | 
— Catherine, I have cleaned the room for you. 
 — Thanks. You ______ it. I could manage it myself.
| A.needn’t do | B.needn’t have done | 
| C.mustn’t do | D.shouldn’t have done | 
— I’ve taken someone else’s green sweater by mistake. 
 — It ______ Harry’s. He always wears green.
| A.has to be | B.will be | C.mustn’t be | D.could be |