It suddenly occurred to him he had left his keys in the office. (2012·江西，25)
A. whether
B. where
C. which
D. that
网友回答
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。