听力原文：What does maglev look like？ Japanese engineers designed a vehicle that runs in a

听力原文： What does maglev look like？ Japanese engineers designed a vehicle that runs in a cradle-like track or guideway. Magnetic attraction and repulsion pull and push maglev forward. To stop the trains, the magnetic force is reversed, much like airplanes are stopped by reversing the force of the engines. Both types of maglev are quiet, fast, and save. Since maglev rides on air, there is no friction between wheels and rails to make noise or to slow it down. If the external power fails, there is a battery-operated system on the train itself that takes over and brings the cars to a smooth stop.

Maglev could be the answer to our problems. It could become the typical short and middle-distance mass transportation system of the twenty-first century. If it does, we will enjoy many benefits. We will ride in save, fast, quiet trains between cities up to about 500 miles apart in less time than it takes to fly if you include the time for ground transportation. We will conserve precious land because maglev can be built where railroads run, down the middle of existing super-highways or elevated above existing streets and roads. And we will probably save money, too. According to a German estimate, a mile of two-way track will cost about nine million dollars whereas a mile of interstate highway costs about 25 million dollars in the United States.

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A．Because it is designed like a cradle.

B．Because it is pulled and pushed by magnetic attraction and repulsion.

C．Because it runs on air.

D．Because there's no friction between wheels and rails.