一、述词过去完成的是形式
我们来看下面的句子：
1. I had painted the wall.
2. Mary had gone.
上面这两个句子中的述词串都是由 had + 主要述词的过去分词（或者叫被动分词 past participle）组成的，这样的结构我们称为述词的过去完成式。
二、述词过去完成式表达的涵义
3. When Tom left, he had been in China for 10 years.
4. Jerry didn't want to give up. She had spent more than 6 months on that project.
5. Jack had written two books on fishing and he was working on another one.
6. Yesterday was the worst day I had ever had.
上面这 4 个句子中的过去完成式表达某事在过去某个时间点之前已经完成。
7. I