Question

完形填空

Milan, the second largest city of Italy, has won an undesirable(不受欢迎的)world record．　　1　　 the 54 big cities studied by the World Health Organization and the United Nations, Milan was considered to have the worst air pollution．According 　　2　　 these two 10 year studies, the level of air pollution in Milan is twice as high 　　3　　 the levels in Paris and Beijing and three times 　　4　　 in Tokyo and London, and four times that in New York．The reason 　　5　　 Milan’s bad pollution, to some experts, is that the city lies in a valley 　　6　　 holds back the poisonous gases．　　7　　 Milan has taken some measures to lower the level of 　　8　　, the situation is still worrying．People joke to each other, “If you traveling to Milan, be sure to 　　9　　 your gas mask(面具)．”In order to reduce the use of private cars, in 1979, the authorities in Milan began an interesting experiment：passengers in the city buses did not have to pay 　　10　　 their tickets．

Answer 1

答案：
解析：

1．Of　2．to　3．as　4．those　5．for　6．that/which　7．Though　8．pollution　9．bring　10．for