過去完成時(had done)

　　①表示在過去的某個時間或動作以前已經(jīng)完成的動作或已經(jīng)存在的狀態(tài)。就是我們常說的"過去的過去"。

　　Until then, his family hadn't heard from him for six months.

　　到那時為止，他家里已經(jīng)有六個月沒得到他的消息了。

　　②表示從過去的過去開始，持續(xù)到過去的動作或情況，并且有可能會繼續(xù)延續(xù)下去。此時經(jīng)常用延續(xù)性動詞。

　　By the time I left the school, he had taught the class for 3 years.

　　到我畢業(yè)時,他已經(jīng)教那個班三年了.

　　過去完成進行時：had been doing

　　表示從過去的過去開始，持續(xù)到過去的動作或情況，期間一直有規(guī)律的在進行、不曾間斷，并且有可能會繼續(xù)延續(xù)下去。此時經(jīng)常用延續(xù)性動詞。

　　例：The old clock had been being taken apart of and fixed up again for several times by my 10-year old son before I came back home.

　　我回到家之前，我10歲大的兒子已經(jīng)把這個舊鐘表拆卸并重新組裝了好幾回了。

　　過去將來完成時：(would have done)

　　表示到過去將來某一時間已經(jīng)完成的動作，并且對過去將來那一時間點產(chǎn)生影響。

　　例：I believed by the end of that year an advanced version of that software would have been developed, but I was wrong.

　　我堅信到那年年底為止，那個軟件的新版本將被開發(fā)出來。但是我錯了。

　　表示動作從過去某一時間開始一直延續(xù)到過去將來某一時間，并且有可能繼續(xù)延續(xù)下去。

　　例：He told me that by the end of the year he would have lived there for thirty years.

　　他告訴我，到那年年底為止他將已經(jīng)在那里住了三十年了。