The air quality in the city, ______ is shown in the report, has i_英语解答

The air quality in the city, ______ is shown in the report, has improved over the past two months.
A. that B. it C. asD. what
四个选项如何区分

人气：324 ℃　时间：2020-02-05 18:09:51

解答

C
这是as 引导的非限制性定语从句,as 代替整个主句,B,D 不是关系词,而that 不可引导非限制性定语从句