【题目】Air pollution is ________ most Chinese people are concerned about nowadays, because their health is being threatened.
A.thatB.why
C.whatD.how
在线课程【答案】C
【解析】
考查表语从句。句意：空气污染是现在大多数中国人关心的问题，因为他们的健康正受到威胁。此处be动词后面是表语从句，从句缺少引导词，谓语动词短语are concerned about缺少宾语，所以所填词要起双重作用，应填what，故选C。