过去完成进行时
had been + 动词的现在分词。
用法：表示一直持续到过去某个时间的行为动作，此行为动作或刚结束、或还没结束(可以从上下文看出)。这一时态经常与一般过去时一起使用。例如：
When he came in, I had been trying to repair the TV for a couple of hours. 他进来的时候，我一直在努力修理电视机好几个小时了
The roads were dangerous. It had been raining for two whole days. 道路很危险。雨一直下了两整天。
They were tired because they had been digging since dawn. 他们累了，因为从天亮开始他们就一直在挖。
The boy was delighted with the new mountain bike. He had been hoping for one for a long time. 那男孩得到一辆新山地自行车很高兴。很长时间来他一直希望有一辆。
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