Câu hỏi:

Read the following passage and mark the letter A,B,C or D to indicate the correct answer to each of the questions.

Rivers are one of the world's most important natural resources. Many cities are on large rivers, and (23)……… every country has at least one river that plays an important part in the lives of its people. Besides transportation, rivers (24)……… food, water for crops, water to drink, and opportunities for recreation for people who live a long their banks. And in order to get water for crops, engineers sometimes build a dam (25)……. 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 electricity for homes and industries. However, the water often becomes (26)…….. when cities on river banks grow in size and the number of industries increases. We are learning that it is necessary to keep rivers clean if we to enjoy the (27)…….of the natural resources Many cities are on large rivers, and (23)……… every country has at least one river that plays an important part in the lives of its people.

Many cities are on large rivers, and (23)……… every country has at least one river that plays an important part in the lives of its people.