6．London has a population of over 7，000，000．From about the year 1800 until World War Ⅱ，London was the biggest city in the world．But now there are many cities which are much bigger than it．London is famous for many things．Tourists come from all over the world to visit its famous buildings and hear the famous clock，Big Ben．Like many big cities，London has problems with traffic and pollution which stop the city from developing．Over one million （百萬） people a day use the London underground，but there are still too many cars on the streets．The air isn't clear，but it is anyhow cleaner than it was 100 years ago．For me，the best things about London are the parks．There are five in the city center．But my children's favorite place is Hamleys，the biggest toy shop in the world．
（1）What's the Chinese for"underground"in the passage？
A．隧道
B．地鐵
C．地下
D．通道
（2）When was London the biggest city in the world？
A．In 1750．
B．In 1850．
C．In 1950．
D．In the 21st century．
（3）What's Big Ben in London？
| A．It's a toy shop． |
B．It's a park． |
| C．It's a clock． |
D．It's a museum． |
（4）How many people use the London underground every day？
A．Over half of its population．
B．Over three quarters of its population．
C．Over 100，000．
D．Over 1，000，000．
（5）How was the air in London 100 years ago？
A．It was much cleaner than it is now．
B．It was the same as it is now．
C．It was the cleanest in the history of London．
D．It was not as clean as it is now．
