阅读下列短文, 从所给的四个选项中, 选出最佳答案。　　 　　

　　    Milan, the second largest city of Italy, has won an undesirable　　 (不受欢迎的) world record. Of the 54 big cities studied by the World　　 Health Organization and the United Nations, Milan was considered to　　 have the worst air pollution.　　

　　    According to these two 10-year studies, the level of air pollution　　 in Milan is twice as high as the levels in Paris and Beijing and three　　 times those in Tokyo and London, and four times that in New York.

　　     The reason for Milan's bad pollution, according to the scientists,　　 is that the city is situated in a valley that holds back the poisonous　　 gases.

　　     Though Milan has taken some measures to lower the level of　　 pollution, the situation is still worrying. People joke about each　　 other, "If you're travelling to Milan, be sure to bring your gas mask."　　 　　

(1)  Which is not mentioned in the passage?  

[    ]

A. The reason for the air pollution in Milan.　　  

B. The measures taken by Milan to solve the problem.   

C. The city's air regarded to be worst polluted.  

D. The conclusion that the air in Milan was badly polluted.　　   

(2)  Which of the following correctly shows the level of air pollution 

in Milan? 

[    ]

　　  A.  　　 　　B.  　　 

    C.  　　     D.     

(3)  Why is the air pollution in Milan so serious?

[    ]

A. Because the city lies in a place where it is difficult for   polluted air to move away.

B. Because too many cars are being driven in the city.

C. Because the city has some mountains. 

D. Because Milan has taken some worrying measures.  

(4) This passage tells us __________. 

[    ]

A. it is quite easy to breathe the air in Milan 　　   

B. it is dangerous to breathe the air in Milan 　　   

C. it is impossible to travel in Milan without a gas mask 　　   

D. it is funny to travel in Milan with a gas mask