3. AA-cell battery:5号电池
4. at least not the kind of engine used to pull typical train cars along steel tracks: 至少不是沿着轨道拉动典型的火车车厢的那种发动机。
5. the magnetic field created by the electrified coils in the guideway walls and the track combine to propel the train: 由嵌入导向壁内的电磁线圈产生的磁场加上轨道，一起推动火车前进。The magnetic field 和 the track 是句子主语，created by the electrified coils in the guideway walls 是过去分词短语，用作定语，修饰the magnetic field.
练习:
1. Paragraph 3
2. Paragraph 4
3. Paragraph 5
A The Main Components of the Maglev Train System
B High-speed Maglev due to Zero Friction
C The Working Principle of the Maglev Train
D Differences between Polarity and Magnetic Field
E Comparison of Maglev Trains with Traditional Ones
F Maglev with a Powerful Motor
4. Paragraph 6
5. Several countries in the world are using strong electromagnets
6. You can connect a wire to the positive and negative ends of a battery .
7. A unique system of magnetic fields is created by the coils
8. The frictionless maglev train enables you
A to develop a maglev train rail system
B To explain why maglev trains are faster
C to pull and push the train forward
D to create a magnetic field
E to experiment with the maglev train
F to travel from Paris to Rome in about two hours
答案与题解：
1. 第三段了举了磁浮列车的三个组成部分，动力源、金属线圈和此贴。选项A 概括了第三段列的内容。
2. E 第四段就磁浮列车和传统火车进行了比较：磁浮列车没有发动机而传统火车有发动机。选项C用comparsion 来概括是准确的。
3. C 第五段比较详细的介绍了为什么磁浮列车会向前运动，也就揭示了磁浮列车的工作原理。
4. B 在第五段解释了磁浮列车浮起和向前运动的原理之后，作者在第六段中进行了磁浮列车速度奇快的原因：去除了传统火车的车轮于铁轨的摩擦。
5. A 选A 的依据是本文第一段第一句：A few countries using powerful electromagnets to develop high-speed trains, called maglev trains.
6.D第二段说，把电线与干电池相连接就能产生一个小磁场，而磁浮列车的运动原理与此相同。第二段第四句是选择D的依据。
7. C第五段的第二句，即“0nce the train is levitated，power is supplied to the coils within the guideway w
