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完成的動作或已經存在的狀態(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完成的動作，并且對過去將來那一時間點產生影響。
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在那里住了三十年了。