—The light in the office is still on.
—Oh, I forgot
A. turning it off
B. turn it off
C. to turn it off
D. having turned it off
网友回答
A. turning it off
B. turn it off
(答案→)C. to turn it off
D. having turned it off
解析：分析forget doing sth. 意为“忘了曾经做过某事”，forget to do sth. 意为“忘记去做某事”。