注意情態(tài)動詞完成式的用法有兩方面的含義：
1.表示已經(jīng)發(fā)生的情況
(1)must have +過去分詞，表示對已發(fā)生情況的肯定推測，譯為“(昨天)一定……”。如：
My pain must have been apparent the moment I walked into the room, for the first man I met asked sympathetically: “Are you feeling all right?”
(2)cant/couldn’t have +過去分詞，表示對已發(fā)生情況的否定推測，譯為“(昨天)一定沒……”。 如：
Mary couldn’t have received my letter; otherwise she would have replied before now.
(3)may/might have +過去分詞醫(yī)學(xué)全在,線gydjdsj.org.cn，表示對已發(fā)生的事情做不肯定、可能性很小的推測，或事實上根本沒發(fā)生，譯為“也許……”。如：
At Florida Power’s Crystal River plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.
2.表示虛擬語氣
(1)needn’t have+過去分詞，表示做了不必做的事，譯為“其實沒必要……”。如：
As it turned out to be a small house party, we needn’t have dressed up so formally.
(2)should /should not have +過去分詞，表示應(yīng)該做某事但實際上未做，或本不應(yīng)該做但實際上做了, 譯為“本(不)應(yīng)該……”。如：
I regret having left the work unfinished; I should have planned everything ahead carefully.
(3)ought to have+過去分詞，表示動作按理該發(fā)生了醫(yī)學(xué)全在,線gydjdsj.org.cn，但實際上未發(fā)生，譯為“該……”，與should的完成式含義類似。如：
The porter ought to have called the fire-brigade as soon as he saw the fire in the stock, which went up in smoke.
(4)could have+過去分詞，表示過去本來可以做但卻未做，譯為“完全可以……”。如：
What you said is right, but you could have phrased it more tactfully.
(5)may/might have + 過去分詞，表示過去可以做但實際未做，譯為“(那樣)也許會……”。如：
It might have been better to include more punchy statistics and photos of equipment in the introduction to further assist first-time office automation managers.
