8.2 forget doing/to do

forget to do　忘記要去做某事?！?未做)
　forget doing　忘記做過某事?！　?已做)
　The light in the office is stil on. He forgot to turn it off.
　辦公室的燈還在亮著，它忘記關(guān)了。(沒有做關(guān)燈的動(dòng)作)
　He forgot turning the light off.
　他忘記他已經(jīng)關(guān)了燈了?！　　?( 已做過關(guān)燈的動(dòng)作)
　Don't forget to come tomorrow.
　別忘了明天來?！　　　　　　　?(to come動(dòng)作未做)

典型例題
　---- 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 可知燈亮著，即關(guān)燈的動(dòng)作沒有發(fā)生，因此用forget to do sth.
而forget doing sth表示燈已經(jīng)關(guān)上了，而自己忘記了這一事實(shí)。此處不符合題意。