in the garden for an hour the girl suddenly realized she had forgot locking her car door

问题补充：

in the garden for an hour, the girl suddenly realized she had forgot locking her car door.

A. Reading

B. To read

C. Having read

D. To have read

答案：

A. Reading

B. To read

(答案→)C. Having read

D. To have read

解析：read的逻辑主语是句子的主语the girl , 且两者之间为主动关系, 所以用ing形式作状语。又根据for an hour可知，read已持续了一段时间，即read先于realized，故要用ing形式的完成式作状语。