Rivers are one of our most important natural resources. Many of the world’s great cities are ______ (locate) on rivers, and almost
_______ country has at least one river flowing through it that plays
________ important part in the lives of its people.
Since the beginning of history, people _______ (use) rivers for transportation. The longest one in the United States is the Mississippi, and the lifeline of Egypt is the Nile.
_________ transportation, rivers give water to drink, water for crops, and chances for fun and recreation for the people
______ live along their banks.
However, large cities and industries that are located on rivers often make problems. As the cities grow _______ size and industries increase in number, the water in the rivers becomes
________ (pollute) with chemicals and other materials. People are learning the
_________ (important) of doing more to keep their rivers clean
________ they want to enjoy the benefits of this natural resource.