一、情態(tài)動(dòng)詞表推測(cè)的三種形式1.情態(tài)動(dòng)詞+動(dòng)詞原形，表示對(duì)現(xiàn)在某動(dòng)作或狀態(tài)的推測(cè)，比如must do，can’t be等。例：It can’t be true.這不可能是真的。2.情態(tài)動(dòng)詞+動(dòng)詞進(jìn)行式，表示推測(cè)某動(dòng)作可能正在進(jìn)行，比如must be doing等。例：Lily must be doing her homework now.莉莉現(xiàn)在一定是在做作業(yè)。3.情態(tài)動(dòng)詞+動(dòng)詞完成式，表示對(duì)過去行為或動(dòng)作的推測(cè)，比如must have done等。例：He must have misunderstood me.他一定是誤解了我。
二、情態(tài)動(dòng)詞表推測(cè)的具體含義不同的情態(tài)動(dòng)詞與行為動(dòng)詞搭配，其具體含義會(huì)有所不同。這里，我們主要針對(duì)"情態(tài)動(dòng)詞+have done"結(jié)構(gòu)，詳細(xì)講解其含義。
1.must have done：推測(cè)某事必定已經(jīng)發(fā)生，只用于肯定句，否定形式用can’t have done。例：The light is on.Father must have come back.燈亮著，爸爸一定已經(jīng)回來了。
2.could have done：對(duì)已發(fā)生的事的可能性進(jìn)行推測(cè)。例：The dictionary has disappeared.Who could have taken it?字典不見了。會(huì)是誰拿了呢?could have done還可以表示某事本來可能發(fā)生卻未發(fā)生。例：I could have slept for long,but Ididn’t.我本來可以睡的時(shí)間長一點(diǎn)兒，但是我沒有。
3.can’t/couldn’t have done：表示某事不可能已經(jīng)發(fā)生，couldn’t have done語氣更委婉。例：She can’t have gone to school.It’s Sunday.她不可能去上學(xué)了。今天是星期天。
4.may/might have done：推測(cè)某事可能已經(jīng)發(fā)生，might have done所表示的可能性更小。例：Polly is very late.She may have missed her train.波莉到現(xiàn)在還沒有來。她可能是誤了火車。
5.should/ought to have done：表示某事本?該發(fā)生卻未發(fā)生，含有責(zé)備、遺憾的意味。例：She should have arrived here by now.她現(xiàn)在應(yīng)該已經(jīng)到這兒才對(duì)啊。6.shouldn’t/oughtn’t to have done：表示某事本不應(yīng)該發(fā)生卻已經(jīng)發(fā)生，含有責(zé)備的意味。例：You oughtn’t to have spoken to them in that way.你不應(yīng)該以那種方式對(duì)他們講話。7.need have done：表示過去有必要做卻沒有做，含有責(zé)備的意味。例：You need have practiced your spoken English more often.你本來應(yīng)該多練習(xí)英語口語的。8.needn’t have done：表示做了不必要做的事。例：There was plenty of time.She needn’t have hurried.那會(huì)兒時(shí)間還很多，她沒必要那樣匆忙。
表推測(cè)時(shí)，英語中只使用must,may,might,may not和can’t。這五個(gè)表達(dá)的語氣依次遞減：
must:一定(語氣肯定)
may：也許(不很肯定)
might：或許(比may語氣更弱)
may not：也許不(表否定)
can’t：一定不(must的反義)
推測(cè)現(xiàn)在的事情用must,may,might,may not和can’t+do或be
e.g.She must be at home now.
The boy may play now.
推測(cè)過去的事情用must,may,might,may not和can’t+have done
e.g.She might have been ill yesterday.
He must have hold the party.
注意：表推測(cè)的must,may,might,may not和can’t是不可以與I think...連用。因?yàn)镮 think...已有推測(cè)的含義，故不能連用。
