It suddenly occurred to him he had left his keys in the office.A. whether B. where C. whi

问题补充：

It suddenly occurred to him he had left his keys in the office.

A. whether

B. where

C. which

D. that

答案：

A. whether

B. where

C. which

(答案→)D. that

解析：考查固定结构。固定结构it occur to sb that…某人突然想去某事；it是形式主语，真正的主语是that引导的主语从句。That没有任何意思只是在句中起引导作用。句意：他突然想起他把钥匙忘记在办公室里了。故D正确。