听力原文： The United States operates under a federal system of government. Under the federal system，power is divided between the central government and the states. The central government is given specific powers. These powers are named in the Constitution. Powers that are not assigned to the central government in the Constitution belong to the states. The central government can pass laws that affect trade between states. The central government can also make treaties with foreign countries. It has the power to print money. The Constitution gives the central government these powers. These powers belong to the central government only. However，the states have many powers that the central government cannot control. For example，a state is allowed to tax people who live and work in the state. The central government cannot put a limit on the amount of money that a state taxes its people. Many people feel that the federal system has many good points. One good point is that it restrains the power of the central government. The central government cannot become too powerful. Another good point is that the central government makes sure that the bigger states don't become too powerful. Under the Constitution，all states are treated equally. The laws of the central government do not favor one state over another. (30)