I.1a away

2a dissolve

3d to seeing

4a because

5b as

6c air pollution

7c who

8a funnel-shaped

II.9 have

10 visiting

11 is spoken 

12 worked

III.18 No,it isn't

19 Natural gas used for heating homes and cooking

 20 Natural gas is used chiefly as a direct source of energy

21 it comes from all over the country from the gas fields below the North sea

22 It will run out during the 21st century

IV 13F 

14F

15T

16F

17T

V 23 I wish I could speak Spanish

24 Mr Robinson,who wants to save money for a new house, works very hard

25 If I weren't very busy, I could go with you

26 Tom isn't tall enough to reach that picture on the wall

27 Miss Lan apologized for being late

28 what bout going to the cinema?

VI. 29 farmers protect the land to change their crops year to year

30 The buses are usually stopped before midnight