That hazy（雾霾）weather has hit 104 cities in middle-east China lately makes citizens well aware of
a terrible problem China is faced with.
A. what
B. how
C. which
D. that
网友回答
(答案→)A. what
B. how
C. which
D. that
解析：句意：最近席卷中国东部104个城市的雾霾天气使公民意识到中国面临一个多么严重的问题啊。Of后面是宾语从句，宾语从句用感叹句，修饰a terrible problem用what，选A。