從零開始學語法：如何表達本來該做某事？
should have done
“should have + 動詞的完成式”表示本應該做而實際上沒有做，它的否定形式表示某種行爲本不該發生但卻發生了。有責備的意味。
You should have started earlier, but you didn't.
你本應該早點兒出發，但是你沒有。
You should have washed the wound.
你應該已經洗好了傷口。
She shouldn't have taken away my dictionary, for I wanted to use it.
她本不應該拿走我的詞典，因爲我要用它。
You shouldn't have been so rude to him.
你本不應該對他那麼粗魯。
注：“should have + 完成式”雖然可以表猜測，但因爲會造成歧義，應少用。
ought to have done
1、“ought to have + 動詞的完成式”表示過去應做某事而實際未做，它的否定形式表示本不應該做某事卻做了（用法和should相同）。
You ought to have helped him, but you didn't.
你本應該幫助他但你沒有。
You ought to have studied harder.
你本應該更努力學習的。
He ought not to have stopped his work halfway.
他本不應該做這項工作時半途而廢。
He oughtn't to have done that.
他本來就不該做那件事。
2、“ought to have + 動詞的完成式”還可以用來表猜測。
They ought to have arrived by now.
現在他們想必已經到達。
If he had started at nine o'clock, he ought to have been in London by eleven o'clock.
如果他在九點出發，那他十一點鐘該到達倫敦了。
