Rivers are one of the world’s (1)____most__ important natural resources. Many cities are on large rivers and almost every country has at least one river that (2)____plays__ an important part in the lives of its people.
Besides transportation, rivers provide food water for crops,water to drink, and opportunities for people (3)____who__ live along their banks.And in order to get water for crops, engineers sometimes build a dam across a river and let water become a lake behind the dam. Then people can use their water notonly to irrigate fields but also to make (4)electricity____ for homes and industries.
