过去完成进行时及其结构是什么？

过去完成停止时是英语中一个复杂的时态，它凡是用来描述在过去某个时间点之前不断在停止的动做或形态。它的构造由过去完成时和停止时两个时态构成，详细如下：

必定句：主语 + had been + 如今分词 + 其他成分

例如："He had been studying for three hours before he finally took a break."

否认句：主语 + had not been + 如今分词 + 其他成分

例如："She had not been working at the company for very long before she was promoted."

疑问句：Had + 主语 + been + 如今分词 + 其他成分？

例如："Had they been waiting for us long before we arrived?"

过去完成停止时凡是用在时间状语从句中，例如："I had been working all day before I realized it was already dark outside." 它也能够用来描述两个动做在过去某个时间点之前同时停止，例如："She had been cooking dinner while he was watching TV."

需要留意的是，过去完成停止时其实不常用，凡是只在需要十分切确的时间描述时利用。在日常英语中，过去完成时和停止时的组合凡是足以满足表达需要。

因而，进修过去完成停止时的构造和用法能够帮忙我们更好天文解和运用英语中的各类时态，进步我们的英语表达才能。