It years ago when the incident took place, and I nearly forget it.
A. would have been
B. should have been
C. ought to have been
D. must have been
网友回答
A. would have been
B. should have been
C. ought to have been
(答案→)D. must have been
解析：考查情态动词+完成式的用法：句意：那一定是在很多年前发生的事情，我几乎要忘了。Must have done过去一定做了，would have done过去会做但是没有做，should have done本应该做却没做，ought to have done过去本应该做却没有做，选D。