These years you can see many underground railways are being built in some big cities. Underground railway is both convenient and fast. The underground railway is also called “the tube”,“the subway”or “the underground”. There're lifts for you to go up or down. The trains' doors open and close automatically. In Shanghai，during rush hours the underground arrives at the station every two minutes. But with too many people taking the underground, people find it really too crowded. Maybe Shanghai needs more underground railways.
注释:
1) Many underground railways are being built.许多地铁正在建造中
2) rush hours上下班高峰时段
3) with more and more people taking the underground随着乘地铁的人越来越多
4) are being build建造中