15.  B. off

16. C. few - much

17. B. met - was

18. C. is - is

19. D. faucets

20. C. natural resources

21. B. going

22. B. wastes

23. A. down

24. A. energy

25. C. off

26. A. Nevertheless

27. D. and

28. D. effective

29. C. instead of

30. C. doesn't

II.

1. Why should we save energy?

2. We should use energy-saving light bulbs to save electricity.

3. Electricity, gas and water are necessities.

4. China' s market accounts for 50% of the total income.

5. Please turn off the light before leaving (a place).

6. Though I would like to have a new backpack, I don't have enough money to buy one.

7. In spite of the freezing weather, he went swimming.

8. Illuminating accounts from 15% to 20% of the electricity bill.

9. My trip lasts for a week.

10. My brother is a teacher working at a secondary school.

III/

1. ordinary

2. plane

3. pipe

4. profitable

5. purpose

6. receive

7. regularly

8. replace

9. label

10. household

IV/

1. Could you lend me your pen?

2. What is Minh doing while Ha looks for the newspaper.

3. Did you go to the countryside last week?

4. How can I help you?

5. How were you yesterday?

6. How high is that mountain?

7. Is baseball your favoutite sport?

8. How often do you go to the concert?

9. How do most children feel coming to see a dentist?

10. Would you like to join our badminton team?

V/

1. off => on

2. on => about

3. switching => switch

4. about => of

5. Because => Therefore

6. are => is