21. B
22. A
23. D
24. B
EX 3:
1. E
2. B
3. D
4. A
5. C
EX 4:
1. Does
2. Will
3. Take
4. Many
EX 5:
1. How can I get to the zoo?
2. You shouldn't drink cold water because you may have a sore throat.
3. I got to my hometown by motorbike.
4. There are four seasons in the North of Vietnam.
5. You must wait the green light.