题目内容：

The world’s first subway was built in London in 1863. At the time，the government was looking for a way to reduce traffic problems in the city of London. The poor areas of the city were so crowded with people that it was almost impossible for horse carriages to get through. The city officials were interested in trying to make it possible for workers to live outside of London and travel easily to work each day. If people had a cheap and convenient way that they could depend on to go to and from work, they would relocate their homes outside of the city. This would help ease(减轻) the pressure of too many people living in the poor parts of London. From these problems，the idea of the London Underground，the first subway system，was born.

The plans for building the Underground met with several problems and delays，but the fast track was finally opened in January 1863. A steam train pulled the cars along the fast underground track which was 6 kilometers (3.7 miles) long. About 30，000 people got on the subway the first day. Riders were treated to comfortable seats (standing up while the train was moving was not allowed)，and pleasant decorations inside each of the cars. However, the smoke from the engine soon filled the air in the tunnels with ash and soot(煤灰), as well as chemical gases. Fans had to be put in the tunnels later to keep the air clean enough for people to breathe. Even with its problems，riding in the Underground did catch on. It carried 9 million riders in its first year.

1.What led the British government to build the London Underground？

A. Traffic jams and pollution.

B. Population and pollution.

C. Overcrowding and traffic jams.

D. The poverty and subway problems.

2.How did the London Underground solve the smoke problem？

A. It made the tunnels larger.

B. It put fans in the tunnels.

C. It cleaned the chemical gases in the tunnels.

D. It reduced the number of passengers riding in the train.

3.The underlined phrase “catch on” most probably means “______”.

A. be troublesome

B. become popular and fashionable

C. keep up with

D. seize

4. Which of the following is TRUE？

A. To relocate the workers’ homes outside London，the government built the subway.

B. There were so many problems and delays that in 18th century the first subway opened.

C. The subway greatly eased the pressure of traffic.

D. There were not enough seats for the passengers the first day the subway opened.