Exercise 6. Choose the correct word A, B, C or D for each gap to complete the following passage.

Rivers are (1) ________________ of the world’s most important natural resources. Many cities are on large rivers, and (2) ________________ every country has at least one river that (3) ________________ an important part in the lives of its people.

Besides transportation, rivers (4) ________________ food, water for crops, water to drink, and opportunities for recreation for people who live along their (5) ________________. And in order to get water for crops, engineers sometimes build a dam across a river and let the water become a lake (6) ________________ the dam. Then people can use their water not only to (7) ________________ fields but also to make electricity for homes and industries.

(8) ________________, the water often becomes polluted when cities on river banks grow (9) ________________ size and the number of industries increases. We are learning that it is necessary to (10) ________________ rivers clean if we want to enjoy the benefits of natural resources.

1. A. one

B. ones

C. among

D. those

2. A. most

B. mostly

C. almost

D. about

3. A. takes

B. makes

C. occupies

D. plays

4. A. supply

B. provide

C. distribute

D. bring

5. A. banks

B. shores

C. sides

D. beaches

6. A. behind

B. on

C. below

D. under

7. A. take

B. irrigate

C. drain

D. give

8. A. Moreover

B. Therefore

C. Thus

D. However

9. A. of

B. about

C. in

D. for

10. A. keep

B. get

C. hold

D. maintain