问题补充:
It suddenly occurred to himhe had left his keys in the office. (·江西,25)
A. whether
B. where
C. which
D. that
答案:
A. whether
B. where
C. which
D. that
解析:D
解析It occurs/occurred to sb. that...某人想到/想起。it是形式主语,主语从句成分完整,不能用连接代词which引导,whether与where不符合句意。故选D项。