The air in mountain areas is _that in big cities

问题描述:

The air in mountain areas is _that in big cities

A.as fresh as B.fresher than C.as dirty as D.dirtier than
答案:fresher than.此题考察形容词的比较级或原级.通常乡村的空气要比城市中的空气新鲜,所以排除A,C,D选项,虽然A选项本身结构是正确的.