1)may(might)have+donesth,can(could)have+donesth表示过去,推测过去时间里可能发生的事情。
Philipmay(might)havebeenhurtseriouslyinthecaraccident.
Philipcan(could)havebeenhurtseriouslyinthecaraccident.
2)musthave+donesth,对过去时间里可能发生的事情的推测,语气较强,具有"肯定","谅必"的意思。
---Lindahasgonetowork,butherbicycleisstillhere.
3)oughttohavedonesth,shouldhavedonesth
本应该做某事,而事实上并没有做。否定句表示"不该做某事而做了"。
Yououghtto(should)havebeenmorecarefulinthisexperiment.
Heoughtnottohavethrowntheoldclothesaway.(事实上已扔了。)
4)needn'thavedonesth本没必要做某事
Idressedverywarmlyforthetrip,butIneedn'thavedoneso.Theweatherwashot.
5)wouldliketohavedonesth本打算做某事
Iwouldliketohavereadthearticle,butIwasverybusythen.