结构
had been Ving
你要知道过去完成时态是had+Vpp,进行时态是be+Ving,两者结合就很好理解了
通过结构来理解时态,这样的好就说明过去完成进行时态是指在过去发生持续了一段时间并且就当时语气是进行中的动作
这一类语句的时间状语十分特殊,是要有特定的时间
列举：
He had been waiting for two weeks． He was still waiting．（有一个表示一段时间的状语）
他已经等了两个星期.他还在等.
Up to that time he had been translating those books．
直到那时他一直在翻译这些书.
He had been writing the letter till two o'clock．
他一直在写那封信到两点钟.
He was thirty years old．He had been gambling since he was ten．（He was still gambling at thirty．）
他三十岁.他从十岁开始就一直在赌博.（三十岁的他仍然赌博.）
He had been standing there in the sun．（没有时间状语）
他一直站在太阳底下.
He had been thinking about his marriage．（没有时间状语）
他一直在对他的婚姻思考.
不过这种时态并不一定表示这个过去动作将持续下去：
He came back at seven．He had been waiting for her two hours．（At seven he did not wait any more．）
他在七点回来了.他等了她两个小时.（七岁的他不想再等了.）
He stopped swimming．He had been swimming for the last three hours．
他停止了游泳.他已经在过去的三小时内游泳.
