V. Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 23 to 28. (1, 5 points) Rivers are one of the world's (23) _____ important natural resources. Many cities are on large rivers, and almost every country has at least one river that (24) _____ an important part in the lives of its people. Besides transportation, rivers provide food, water for crops, water to drink, and opportunities for recreation for people (25) _____ live along their banks. And in order to get water for crops, engineers sometimes build a dam across a river and let the water become a lake behind the dam. Then people can use their water not only to irrigate fields but also to make (26) _____ for homes and industries. (27) _____, the water often becomes polluted when cities on river banks grow in size and the number of industries increases. We are learning that it is necessary (28) ________ rivers clean if we want to enjoy the benefits of the natural resources. 23. A. more B. much C. many D. most 24. A. takes B. makes C. occupies D. plays 25. A. who B. which C. what D. where 26. A. electric B. electrician C. electricity D. electrical 27. A. Moreover B. Therefore C. Thus D. However 28. A. keeps B. to keep C. will keep D. is keeping