过去完成时和过去完成进行时
>过去的两个时态是过去完成时和过去完成进行时。这两种时态之间有细微的差别，但都用于谈论发生在过去另一个时间点之前的行为。
Past Perfect过去完成时
有两种过去时态用来描述发生在过去另一个时间点之前的事情。用过去完成时谈论发生在某事发生之前的某个时间点的事件。
Tom had interviewed five times before he got his first job.She had already eaten by the time they arrived.
Past Perfect Continuous过去完成进行时
过去完成进行时用来表达在过去重要的事情发生之前，某事已经进行了多长时间。
Jane had been studying for four hours when he came home.Jack had been driving four over six hours when he finally pulled over to have lunch.
Past Perfect Structure过去完成时的结构
Positive肯定句
Subject + had + past participle
I, You, He, She, We, They had finished before I arrived.
Negative否定句
Subject + had + not (hadn\'t) + past participle
I, You, He, She, We, They hadn\'t eaten before he finished the job.
Questions疑问句
Question word + had + subject + past participle
What -> had he, she, you, we, they thought before I asked the question?
Past Perfect Continuous Structure过去完成进行时结构
Positive肯定句
Subject + had + been + verb + ing
I, You, He, She, We, They had been working for two hours when she telephoned.
Negative否定句
Subject + had + not (hadn\'t) + been + verb + ing
I, You, He, She, We, They hadn\'t been paying attention for long when he asked the question.
Questions疑问句
Question word (often \'How long\') + had + been + subject + verb + ing
How long -> had he, she, you, we, they been working before he arrived?