What is the longest river in the United States? 美国最长的河是什么河？

　　It is the Mississippi River. 密西西比河。

　　In fact, the Mississippi River is the longest river in north America. 事实上，密西西比河是北美最长的河流。

　　The Mississippi River passes through 31 states of the United States. 密西西比河流经美国的31个州。

　　The Mississippi River is a major road for both humans and birds. 它是人类和鸟类的主要通道。

　　The river carries 46 percent of the grain in the United States. 它运载着美国46%的粮食。

　　Also, 40 percent of birds in America fly along the Mississippi River every spring and fall. 每年春秋，美国40%的鸟类都飞往密西西比河沿岸。

　　Also, the Mississippi River is very important, because over four million people drink its water. 密西西比河非常重要，因为它为400多万人提供饮用水。