题目内容：

阅读下面材料，在空白处填入适当的内容(1个单词)或括号内单词的正确形式。

As populations increased in large cities in 1. nineteenth century, building subway lines was a way 2.(move) people from one area of a city to another quickly and efficiently. The first major subway system, the London Underground, 3.(start) in 1873 using steam trains. Subways caught on quickly in London. From 1896, it was changed in favor of an electrical system. Today’s subways around the world now work on 4.(electrical). Passengers can rely on the regular schedule of subway trains while 5.(avoid) traffic on busy city streets.

Two of the world’s earliest subways were built in Paris and New York. When the Paris Metro opened on July 19, 1900, citizens were proud of the 6.(impress) and beautifully decorated station entrances.7. the first New York subway consisted 8. only 14.5 kilometers of track in 1904, today, it is the world’s largest subway system.

Today, subways are still popular with passengers. The Tokyo subway is the 9.(busy) in the world, with 3.2 billion riders a year. Close behind 10.(be) subways in Moscow(2.4 billion), Seoul (2.1 billion), and New York City (1.6 billion).