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[audioFiles]audio_ezf_m_0063(20101)[/audioFiles]

游客2023-11-22  53
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答案                                       Airplane Engines
     In 1945 a new type of airplane engine was invented. / It was much lighter and more powerful than earlier engines, / and enabled warplanes to fly faster and higher than ever. / This type of engine was called the jet engine / because it blows a large jet of hot air backwards at high speed. / The first airplane to use the new jet engine was built in Britain / and it began carrying passengers in 1952. / It had two jet engines and flew much higher than petrol-engine airplanes. / At this height the air is thinner and very cold, / and so the airplane can cut through the air more easily. / However, the cabin has to be air-conditioned and has to be at normal pressure / so that the passengers may eat, read and sleep in comfort. /
     Today all long-distance airplanes have jet engines. / The modern jet airplanes are very big and can carry hundreds of passengers on two different floors, / which makes air travel much cheaper.
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