听力原文：Twice a year, all the clocks in the United States are changed by one hour. In the

听力原文： Twice a year, all the clocks in the United States are changed by one hour. In the spring, clocks are moved ahead an hour. This is called daylight savings time. In the fall, clocks are set back an hour to standard time. People remember how to change their clocks by remembering this saying: Spring forward, fall back. It seems Benjamin Franklin was the first person to propose the idea of daylight savings time back in the 1790s. At the time, people thought he was joking. They couldn't believe he was serious. Many years later, during World War I, people realized what an innovative idea he'd had. In the spring and summer, the sun rises earlier. By moving the clock ahead, people can take advantage of the extra daylight and save energy. Energy is an important resource, of course, especially during wartime. The United States operated on daylight savings time during World War I and again during World War II. After that some parts of the country observed daylight savings time and some didn't. Beginning and ending dates varied from place to place. This confusion ended in 1966, when the Congress passed the Uniform. Time Act, standardizing the process and making daylight savings time a federal law. Since then, some lawmakers have proposed that the United States go to year-round daylight savings time.

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A．The Uniform. Time Act.

B．The role of daylight savings time in wartime.

C．Ways to save energy.

D．The history of daylight savings time.