一、“must + have + 過去分詞”表示對過去發(fā)生的事情或狀態(tài)進(jìn)行推測，語氣比較堅定，通常只用于肯定句。如：

　　It must have rained last night, for the ground is wet.

　　You must have been mad to speak to the servant.

　　二、“can / could + have + 過去分詞”表示對過去某種情況的懷疑或不確定。can和could一般用于否定句和疑問句，could的語氣較can弱。如：

　　I didn't see her at the meeting this morning; she can't / couldn't have spoken at the meeting.

　　He can't have finished the work so soon.

　　三、“may / might + have + 過去分詞”表示對已發(fā)生的動作或存在的狀態(tài)進(jìn)行不肯定的推測，might的語氣比may弱一點(diǎn)。這種結(jié)構(gòu)主要用于肯定句和否定句，疑問句改用can或could。如：

　　They may not have known it beforehand.

　　You might have read about it in the papers.

　　四、“need + have + 過去分詞”表示過去做了不必做或不需要做的事情，或過去做某事純屬多余。如：

　　Need they have done it last week?

　　I needn't have bought so much wine—only five people came.

　　五、“should / ought to + have + 過去分詞”表示過去本該做某事但沒做，其否定式表示過去不該做某事但做了，這種句式含有不滿或責(zé)備之意，ought to的語氣比should強(qiáng)一些。如：

　　You ought to / should have studied harder. 你本應(yīng)該更努力學(xué)習(xí)的。（但沒有）

　　He oughtn't to / shouldn't have done that. 他本來就不該做那件事。（可是做了）

　　六、“would ＋ have ＋ 過去分詞”表示對過去的某種情況進(jìn)行猜測，或本來要做某事卻因某種原因未做成，通常用來說明某一情況，但不像用should或ought to那樣含有責(zé)備之意。如：

　　I guess the poet would have been about twenty when she wrote her first poem.

　　Another worker wouldn't have acted like that.