什么是过去完成进行时？
过去完成进行时是英语中的一种复合时态，用来描述在过去某个时间点之前已经开始并一直持续到另一个过去时间点的动作或状态。它结合了过去完成时和过去进行时的特点，强调在过去某一点开始并一直持续到另一个过去时间点的动作。以下是一些例子，展示了过去完成进行时的用法：
- 从过去到另一个过去时间点一直持续的动作：
- I had been studying English for two hours before I went to bed.（在我上床睡觉之前，我已经学习了两个小时英语。）
- She had been working on the project all week when it was finally completed.（最终完成时，她已经连续一周在做这个项目了。）
- 强调持续性和延续性：
- He had been practicing the piano for months before the recital.（在演奏会之前，他已经练习了好几个月的钢琴。）
- They had been traveling around the world for years before they settled down.（在安定下来之前，他们已经环游世界好几年了。）
- 从过去某一点到另一个过去时间点一直进行的状态：
- She had been living in that city for a long time before she moved to another country.（在搬到另一个国家之前，她已经在那个城市住了很长时间。）
- He had been feeling unwell for days before he finally went to the doctor.（在最终去看医生之前，他已经感到不适好几天了。）
过去完成进行时强调从过去某一点开始，持续到另一个过去时间点的动作或状态，突出动作的持续性和在过去的时间范围内的延续。
1. 过去完成进行时的形式
had been + 现在分词
2. 过去完成进行时的用法
1) 表示持续到过去某时的一个动作
* We had been waiting for him for about an hour by the time he came. 当他来的时候，我们等他有一个小时了。
* How long had it been raining after he left home? 在他离开家后，雨下了有多长时间了？
* She said that she had been listening to radio after school. 她说她放学后一直在听收音机。
* She had been studying for two hours when her classmate came to visit her. 当她的同学来看她的时候，她学习有两个小时了。
* She had been suffering from a bad cold when she took the exam.她在考试之前一直患重感冒。
* Had they been expecting the news for some time? 他们期待这个消息有一段时间了吧？
* Rafael was scolded even though he hadn’t been doing anything wrong. 尽管拉斐尔没做什么错事，但他还是挨骂了。
* I had been looking for it for days before I found it. 这东西我找了好多天才找着的。
2) 这个时态常用于某些从句中
* The doctor asked what he had been eating. 医生问他吃了什么。
* I asked where they had been staying all those days.我问他们那些天是呆在哪儿的。
* They received the parcel that they had been expecting for a long time.
他们收到了他们期待已久的包裹。
