By the time he was twelve, Edison had began to make a living
by himself. 到了十二岁那年，爱迪生开始自己谋生。
Tom was disappointed that most of the guests had left when he
arrived at the party.
汤姆失望了，因为他到达晚会时，大部分客人已经走了。
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 hardly… when 还没等…… 就……。例如：
I had hardly opened the door when I he hit me. 我刚打开门，他就打了我。
had no sooner…than 刚…… 就……。例如：
He had no sooner bought the car than he sold it.
他刚买了这辆车，转眼又卖了。
11.16 用一般过去时代替过去完成时
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。例如：
When she saw the mouse，she screamed. 她看到老鼠，就叫了起来。
My aunt gave me a hat and I lost it. 姑妈给了我一顶帽子，我把它丢了。
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。例如：
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。例如：
Our teacher told us that Columbus discovered America in 1492.
11.17 将来完成时
1） 构成will have done
2） 概念
a. 状态完成：表示某事继续到将来某一时为止一直有的状态。例如：
They will have been married for 20 years by then.
到那时他们结婚将有二十年了。
b. 动作完成：表示将来某一时或另一个将来的动作之前，已经完成的动作或获得的经验。例如：
You will have reached Shanghai by this time tomorrow.
明天此时，你已经到达上海了。
11.18 现在进行时
现在进行时的基本用法：
a. 表示现在（指说话人说话时）正在发生的事情。例如：
We are waiting for you. 我们正在等你。
b. 习惯进行：表示长期的或重复性的动作，说话时动作未必正在进行。例如：
Mr. Green is writing another novel.
他在写另一部小说。（说话时并未在写，只处于写作的状态。）
c. 表示渐变，这样的动词有：get, grow, become, turn, run, go, begin等。例如：
The leaves are turning red. 叶子在变红。
It's getting warmer and warmer. 天越来越热了。
d. 与always, constantly, forever
等词连用，表示反复发生的动作或持续存在的状态，往往带有说话人的主观色彩。例如：
You are always changing your mind. 你老是改变主意。
典型例题
My dictionary ___, I have looked for it everywhere but
still___ it.
A. has lost, don't find B. is missing, don't find C. has lost,
haven't found D. is missing, haven't found.
答案D. 前句是一个仍在持续的状态，应用进行时，由于没有找到，其影响仍然存在，应用完成时，瞬间动词用
于否定式时可用于完成时。
