1.概念：
表示某个正在进行的动作或状态，持续到过去某个时刻，还未完成，一直持续到之后的当前才结束。
2.基本结构：
主语+ had + been + doing +其它
3.例子：
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？
4.特殊含义：
①尚未完成：He had been writing the novel. 他已经在写小说了。（他没写完）
②企图：He had been studying the meaning of this proverb. 他曾经学习过这个谚语。（他曾努力学习过它）
③未得结果：We had been studying what our enemy had said. 我们一直致力于敌人所说的。（但是我们没有理解）
④最近情况：He had been quarrelling with his wife. 他和他的妻子吵了一场架。（最近）
⑤反复动作：He had been asking me the same question. 他一直问我相同的问题。（屡次）
⑥情绪：What had he been doing? 他做了什么？（不耐烦）