過(guò)去完成時(shí)典型例題
　　
The students ___ busily when Miss Brown went to get a book she ___ in the office.　
A. had written, left　B，were writing, has left C. had written, had left　D. were writing, had left
　　
答案D. "把書(shū)忘在辦公室"發(fā)生在"去取書(shū)"這一過(guò)去的動(dòng)作之前，因此"忘了書(shū)"這一動(dòng)作發(fā)生在過(guò)去的過(guò)去，用過(guò)去完成時(shí)。句中when表示的是時(shí)間的一點(diǎn)，表示在"同學(xué)們正忙于……"這一背景下，when所引導(dǎo)的動(dòng)作發(fā)生。因此
　　
前一句應(yīng)用過(guò)去進(jìn)行時(shí)。
注意：　had no … when　　　　　還沒(méi)等…… 就……
had no sooner… than　　剛…… 就……
He had no sooner bought the car than he sold it.