内容：
托福语法举例：过去完成进行时
去完成进行时是由 had been+现在分词构成，因此无人称变化：
I had/I’d been working
they had not/hadn’t been workingwww.Exam
had you been working?
had you not/hadn’t you been working?
凡不能用于进行时的动词均不能有这种时态，但动词want(有时还有wish)除外：
The boy was delighted with his new knife.He had been wanting one fora long time.
男孩对新小刀很高兴。他早就想要一把了。
注意：这一时态没有被动语态，像They had been picking ap-ples(他们一直在摘苹果)这样的句子，最近似的被
动式是Ap-ples had been picked(苹果已摘完)，实际上这两种说法意思并不相同。(参见下面B3。)
B 用法
过去完成进行时与过去完成时之间的关系，同现在完成进行时与现在完成时之间的关系相同。(参见第192节。)
1 表示动作在所说的过去某一时刻之前就已开始并持续到那一时刻或者在那一时刻之前刚刚停止时，常常可以用
两个时态中的任一个(参见第192节A)：
It was now six and he was tired because he had worked since dawn.
已经6点了，他感到很累，因为他从天亮起一直工作到现在。相当于：
It was now six and he was tired because he had been working since dawn.
那时正是6点，他因从一大早就干活而累了。
