过去完成时
Paul was unconcerned about what he had done.
保罗对自己所做过的事情并不在意。
He felt he had atoned for what he had done to his son.
他觉得他已弥补曾对儿子所做的错事。
A period spent working abroad had done nothing to mellow him.
他在海外工作了一段时间，却没有变得老练。
He was an experienced parachutist who had done over 150 jumps.
他是个经验丰富的跳伞者，已经跳过150多次了。
He said he had done nothing wrong to merit a criminal investigation.
他说他没有做错任何事，不应该受到刑事调查。
“Had done” 是英语中的过去完成时（Past Perfect Tense）结构，由助动词 had +动词的过去分词（如 done, eaten, written）构成。以下是其核心用法和含义：
表示在过去某一时间点或动作之前已经完成的动作，即“过去的过去”。例如：
By 10 a.m.,I had finished my homework.
（到上午10点时，我已经完成了作业。）
→ “完成作业”发生在“10点”之前。
When she arrived, the trainhad left.
（她到达时，火车已经离开了。）
→ “火车离开”先于“她到达”。
常搭配by the time, before, after, until 等时间状语：
By the time he woke up, his roommatehad cooked breakfast.
（他醒来时，室友已经做好了早餐。）
用于与过去事实相反的假设（如 if 从句）：
If Ihad known the answer, I would have told you.
（如果我当时知道答案，就会告诉你了。）
→ 实际“过去不知道答案”。
Shehad left when I called. （过去完成，强调“打电话前离开”）
Shehas left the company. （现在完成，强调“现在已不在公司”）
had done 是一个过去完成时态，表示在过去某个时间点之前已经完成的动作或状态。通常与 before 或 by the time 连用。
在过去完成时态中，had 是助动词，done 是主动词的过去分词形式。
构成：主语 had 过去分词
had done 表示在过去某个时间点之前已经完成的动作或状态。
与过去时态的区别：
过去完成时态还可以用以下结构表示：
例如：I had been studying for 3 hours before I took a break. (我休息前已经学习了3个小时。)
过去完成时态的反义词是过去未完成时态：
例如：I had not finished my homework by the time my friends came. (我的朋友们来之前，我还没有完成作业。)
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