I remembered the door before I left the office but forgot to turn off the lights.A. lockin

问题补充：

I remembered the door before I left the office but forgot to turn off the lights.

A. locking

B. having locked

C. to have locked

D. to lock

答案：

A. locking

B. having locked

C. to have locked

(答案→)D. to lock

解析：句意为：离开 办公室前我记着要去锁门，却忘了关灯。 remember/forget to do sth.记得 /忘记去做某事； remember/forget doing sth.记得 /忘记曾经做过某事。选D。