题目内容：

Rivers are one of our most important natural resources(资源). Many of the world’s great cities are located on rivers, and almost every country has at least one river running through it that plays an important part in the lives of its people.

Since the beginning of history, people have used rivers for transportation. The longest one in the United States is the Mississippi. The lifeline of Egypt is the Nile. To the people of India, the Ganges is great, but it is also important for transportation; ships can travel along it for a thousand miles. Other great rivers are the Congo in Africa and the Mekong in southeastern Asia. The greatest of all for navigation（航海）, however, is the Amazon in Brazil（巴西）. It is so wide and so deep that large ships can go about two thousand miles up it.

Besides transportation, rivers give food to eat, water to drink, water for crops, and chances for fun. In order to increase the supply(供给) of water for crops, engineers sometimes build a dam (大坝)across a river and let a lake form behind the dam. Then people can use the water not only to irrigate(灌溉) their fields but also to make electricity for their homes and industries.

However, large cities and industries that are located on rivers often cause problems. As the cities grow in size and industries increase in number, the water in the rivers becomes polluted with chemicals and other materials. People are learning the importance, however, of doing more to keep their rivers clean if they want to enjoy the benefits of these natural resources.

1.The greatest river for navigation is ________________.

A．the Mississippi	B．the Nile
C．the Mekong	D．the Amazon

2.Which is NOT true according to the passage?

A．Many cities are located on rivers.

B．Almost every country has at least one important river.

C．The Nile is in India.

D．Rivers play an important part in the lives of people.

3.When rivers are dammed, people use the water for __________.

A．keeping the rivers clean

B．making electricity

C．washing clothes

D．irrigation and the production of electricity

4.Most water in rivers is polluted with ___________.

A．people’s drinking water too much

B．people’s swimming in the river too much

C．chemicals and other materials

D．people’s building a dam across a river

5.The best title for the passage is _____________.

A．The Importance of Rivers	B．Rivers in Cities
C．Transportation	D．Natural Resources