【题目】With many cities in China dreadfully blanketed by thick haze, the environmental problem is _____ Chinese people concern most nowadays.
A. what B. which C. where D. when
在线课程【答案】A
【解析】
试题分析：考查关系词。句意：中国的许多城市都被雾霾笼罩，现在环境问题是中国人民最关心的问题。表语从句，what在从句中充当宾语，故选A项。