1)现在完成进行时态 (have/has been + -ing 分词构成): 动作或状态从过去某时开始,继续到现在,可能继续下去,也可能刚刚结束.
I’ve been writing letters for an hour.
I’ve been sitting in the garden.
2)过去完成进行时(由had been + ing分词构成): 过去某个时刻以前一直在进行的动作
I’d been working for some time when he called.
We had been waiting for her for two hours by the time she came.