Read the following passage and choose the most suitable answer to fill in each blank.

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

Besides transportation, rivers  …………..… (3)food, water for crops, water to drink, and opportunities for recreation for people who live along their  ……….. (4) . And ……….(5) get water for crops, engineers sometimes………….…...(6) a dam across a river and let the water ………………(7) a lake behind the dam. Then people use their water not only to irrigate fields …….…(8) to make electricity for home and industries.

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

(1) ..................

• A. 
  resources
• B. 
  goods
• C. 
  possessions
• D. 
  materials