听力原文：

Do you know something about the United States? The United States is a developed country, but it is one of the youngest countries in the world; it’s less than 300 years old. The United States is about the same size as China. It has a much smaller population than China. The United States has a famous river — the Mississippi River. The Mississippi River is 3,767 kilometers long. It’s the fourth-longest river in the world, second only to the Nile in Africa, the Amazon River in South America and the Yangtze River in China. It is the longest river in the whole North America.

答案：1. C