forget to do忘记要去做某事。(未做)
forget doing忘记做过某事。(已做)
The light in the office is stil on. He forgot to turn it off.
办公室的灯还在亮着,它忘记关了。(没有做关灯的动作)
He forgot turning the light off.
他忘记他已经关了灯了。 ( 已做过关灯的动作)
Don’t forget to come tomorrow.
别忘了明天来。 (to come动作未做)
典型例题
---- 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
答案:C。由the light is still on 可知灯亮着,即关灯的动作没有发生,因此用forget to do sth.
而forget doing sth表示灯已经关上了,而自己忘记了这一事实。此处不符合题意。