Cause The vehicles on the road that (1)convey people to and around the city centre caused (2)unbelievable_traffic_jams,_which led to the development of the underground system. Development ●In 1854, an underground railway was decided to be built between Paddington and Farringdon.

●In 1863, the (3)initial_tunnels were opened, which were just beneath the surface of the ground.

●In 1868, the next (4) section of the underground system was opened in the south of London.

●In 1884, the Metropolitan Railway Company and the Metropolitan District Railway (5)linked_up and provided underground service in the middle of the city.

●In 1890, South London Railway opened the first electric underground railway.

●Over the next twenty­five years, six (6)independent deep underground lines were constructed.

●Between 1918 and 1938, many new stations were constructed.

●During World War Ⅱ， the underground system had some unusual uses.

●After 1945, the underground system was (7)enlarged and more lines were added, which helped make the system more (8)user­friendly．

●In 1979, the Jubilee Line was opened in honour of the twenty­fifth (9)anniversary of Elizabeth Ⅱ becoming the queen. Achievements The London underground system is working to transport huge numbers of people every day. The network of the underground system includes (10)twelve lines and now goes twenty­six miles out of central London. 　　

　　Ⅲ.Study­reading

　　Analyze the following difficult sentences in the text.

　　1．Travelling on these lines was not convenient, though, as each line was possessed by a different company, and many were very far from each other.

　　[句式分析]