1.should/ought to have done的含義.“should/ought to have＋過(guò)去分詞”表示“過(guò)去應(yīng)該做謀事卻沒(méi)有做”； “should not/ought not to have＋過(guò)去分詞”表示“作了不應(yīng)該做的事”.含有責(zé)備或遺憾的意思.例如：
You shouldn’t /oughtn’t to have come here alone at such a late hour.你這么晚的時(shí)候本不一該一個(gè)人來(lái)這里的.（實(shí)際是一個(gè)人來(lái)的）
She should/ought to have gone there alone.她本該一個(gè)人去那里的.（實(shí)際上不是）　
2.would have done的含義.would have done“本愿意做某事”,非虛擬語(yǔ)氣時(shí),就是would 情態(tài)動(dòng)詞加動(dòng)詞原形,
have done 就是現(xiàn)在完成時(shí),所以和起來(lái) 就是將來(lái)完成時(shí)的用法
過(guò)去將來(lái)完成時(shí)表示在過(guò)去看來(lái)將來(lái)某時(shí)會(huì)已經(jīng)完成的動(dòng)作.例如：
She said she’d have finished her exams by then.她說(shuō)那時(shí)她會(huì)已經(jīng)考完試了.
He knew he arrived she would have gone home.他知道他到時(shí)她會(huì)已經(jīng)回家了
3.must have done的含義.“must have＋過(guò)去分詞”表示對(duì)過(guò)去的推測(cè),意思是“一定已經(jīng),想必已經(jīng),準(zhǔn)是已經(jīng)….”,只用于肯定句中.例如：
He must have been drinking beer.他肯定一直喝啤酒來(lái)著.
若要表示否定,要用“can’t/couldn’t+ have+過(guò)去分詞”,意思是“不可能”：
The money can’t have been lost there.錢(qián)不可能是在那兒丟的.
should have done“本應(yīng)該做某事”
might have done“可能做過(guò)某事”
could have done“本可以做到某事”
would have done“本愿意做某事”
都是表示與過(guò)去事實(shí)相反.if條件句中的虛擬基本含義相同,只是要注意主從句時(shí)態(tài)一致