预约成功
用一般过去时代替完成时
1) 两个动作如按顺序发生，又不强调先后，或用then，and，but 等连词时，多用一般过去时。
When she saw the mouse，she screamed.
My aunt gave me a hat and I lost it.
2 ) 两个动作相继发生，可用一般过去时;如第一个动作需要若干时间完成，用过去完成时。
When I heard the news, I was very excited.
3) 叙述历史事实，可不用过去完成时，而只用一般过去时。
Our teacher told us that Columbus discovered America in 1492.
过去完成时典型例题
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. "把书忘在办公室"发生在"去取书"这一过去的动作之前，因此"忘了书"这一动作发生在过去的过去，用过去完成时。句中when表示的是时间的一点，表示在"同学们正忙于……"这一背景下，when所引导的动作发生。因此前一句应用过去进行时。
注意：
had no … when 还没等…… 就……
had no sooner… than 刚…… 就……
He had no sooner bought the car than he sold it.
