The air quality in the city， is shown in the report，has improved over the past two months.(2012·福建，23)
A. that
B. it
C. as
D. what
网友回答
A. that
B. it
(答案→)C. as
D. what
解析：句意：正如报告中所表明的，城市空气质量在过去两个月里已经得到改善。考查由as引导的非限制性定语从句。分析题干可知，is shown in the report是非限制性定语从句，因为代词that，it和what不能引导非限制性定语从句，所以排除A、B和D项，答案为C项。