问题
选择题
It suddenly occurred to him ________ he had left his keys in the office.(2012·江西)
A．whether
B．where
C．which
D．that
答案
答案：D
句意：他突然想起他把钥匙落在办公室里了。It occurred to sb that...表示“某人想起……”。it在句中作形式主语，真正的主语是that引导的从句。