先理解过去完成时 （already 只强调“已经”，即使没有already在过去完成时里也已先发生了）
I asked the price of the car,but they had already sold it. 过去完成时发生在“过去的过去”
这在问出这句话“asked”的时间点之前，这车就已“sold”。所以“asked”是一般过去时，而“sold”则是过去完成时。这样的组合很容易就把一件事的时间顺序描述得很清晰。
I ran to the platform quickly,but the train had already left.
在“ran”站台之前，这火车就已经“left”。火车离开已完成，所以使用“had already left”，而我跑到站台则是一个过去发生的事情。
再做课文练习模仿例句（使用after、before改写以下句子）
Did you read the book? Yes, but I saw the film first.
| after |
I read the book after I had seen the film. |
| before |
I had seen the film before I read the book. |
Did you go to the doctor? Yes, but I made an appointment first.
| after |
I went to the doctor after I had made an appointment. |
| before |
I had made an appointment before I went to the doctor. |
Did the boss leave the office? Yes, but he finished work first.
| after |
The boss left the office after he had finished work. |
| before |
The boss had finished work before he left the office. |
Did your wife go out? Yes, but she finished the housework first.
| after |
My wife went out after she had finished housework. |
| before |
My wife had finished housework before she went out. |
Did your teacher give you your exercise book? Yes, but he corrected it first.
| after |
My teacher gave me my exercise book after he had corrected it. |
| before |
My teacher had corrected my exercise book before he gave it to me. |
Did your sister go on holiday? Yes, but she took the examination first.
| after |
My sister went on holiday after she had taken the examination. |
| before |
My sister had taken the examination before she went on holiday. |
Did you buy a new car? Yes, but I sold my old one first.
| after |
I bought a new car after I had sold my old one. |
| before |
I had sold my old car before I bought a new one. |
扩展知识：after / before + 时态
| after 后接完成时 |
before 后接非完成时 |
| 动作B (一般过去时) + after + 主语 + had + 动作A (过去分词) |
主语 + had + 动作A (过去分词) + before + 动作B (一般过去时) |
- I read the book after I had seen the film.
- She went out after she had finished the housework.
|
- I had seen the film before I read the book.
- She had finished the housework before she went out.
|
after → 后面的动作用 过去完成时
before → 前面的动作用 过去完成时
