4. The students need________some new books on Math.
A. to buy B. buy C. buying D. to be bought
5. If you don't work hard, you_______better results.
A. won't get B. don't get C. wouldn't get D. had got
6. They enjoyed the trip to Dalat________their grandparents have lived for a very long time. 
A. which B. where C. when D. that
7. Nam didn't go to school yesterday,_________? 
A. did he B. didn't he C. does he D. doesn't he
8. If people can solve the problems of smoke from vehicles and factories, the air_________pure and fresh.
A. is B. will be C. won't be D. isn't
9. Children should drink milk________it's good for their health.
A. and B. but C. as D. so
10. _________my car repaired, I wouldn't have borrowed yours.
C. If I had had A. Unless I have B. If I had D. If I have
11. The children often ask their parents________going out after finishing homework.
C. into  A. about B. with D. for
12. ________the weather was so bad, they set off for their trip. 
A. Although B. But C. And D. Therefore 
13. My mother bought a lot of stuff________we might need for our house.
A. that B. who C. whose D. when
Giải thích (k cũng đc)