過去完成時(shí)(had done)

　　①表示在過去的某個(gè)時(shí)間或動(dòng)作以前已經(jīng)完成的動(dòng)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(shí)為止，他家里已經(jīng)有六個(gè)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(dòng)作或情況，并且有可能會(huì)繼續(xù)延續(xù)下去。此時(shí)經(jīng)常用延續(xù)性動(dòng)詞。

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

　　到我畢業(yè)時(shí),他已經(jīng)教那個(gè)班三年了.

　　過去完成進(jìn)行時(shí)：had been doing

　　表示從過去的過去開始，持續(xù)到過去的動(dòng)作或情況，期間一直有規(guī)律的在進(jìn)行、不曾間斷，并且有可能會(huì)繼續(xù)延續(xù)下去。此時(shí)經(jīng)常用延續(xù)性動(dòng)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(gè)舊鐘表拆卸并重新組裝了好幾回了。

　　過去將來完成時(shí)：(would have done)

　　表示到過去將來某一時(shí)間已經(jīng)完成的動(dòng)作，并且對(duì)過去將來那一時(shí)間點(diǎn)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(jiān)信到那年年底為止，那個(gè)軟件的新版本將被開發(fā)出來。但是我錯(cuò)了。

　　表示動(dòng)作從過去某一時(shí)間開始一直延續(xù)到過去將來某一時(shí)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。