问题补充：
Once air pollution in most cities, it is hard .
A. rises; dealing with
B. arouses; to be dealt with
C. raises; dealt with
D. arises; to deal with
答案：
A. rises; dealing with
B. arouses; to be dealt with
C. raises; dealt with
(答案→)D. arises; to deal with
解析：考查动词辨析和不定式的用法：句意：在多数城市一旦空气污染产生了，就很难解决。Rise是“上升，上涨，起身”，arouse“激起”，raise“提高，筹集，饲养”，arise“产生，发生”，所以第一空填arise，第二空使用的是：Sb/sth is +adj +to do…句型，其中的不定式用主动表示被动，选D。
