情態動詞（四）

7 情態動詞 have 過去分詞

　　1） may（might） have done sth， can （could） have done sth　表示過去，推測過去時間裡可能發生的事情。

　　Philip may （might） have been hurt seriously in the car accident.

　　Philip can （could） have been hurt seriously in the car accident.

　　2）　must have done sth，對過去時間裡可能發生的事情的推測，語氣較強，具有“肯定”，“諒必”的意思。

　　- Linda has gone to work， but her bicycle is still here.

　　-She must have gone by bus.

　　3） ought to have done sth， should have done sth

　　本應該做某事，而事實上竝沒有做。否定句表示“不該做某事而做了”。

　　You ought to （should） have been more careful in this experiment.

　　He ought not to have thrown the old clothes away.（事實上已扔了。）

　　ought to 在語氣上比should 要強。

　　4） needn't have done sth　 本沒必要做某事

　　I dressed very warmly for the trip，but I needn't have done so. The weather was hot.

　　5） would like to have done sth　 本打算做某事

　　I would like to have read the article，but I was very busy then.

　　8 should 和ought to

　　should 和ought to 都爲“應該”的意思，可用於各種人稱。

　　-Ought he to go？

　　-Yes. I think he ought to.

　　表示要求，命令時，語氣由 should（應該）、had better）、must（必須）漸強。