标志词：already,yet,before,recently,lately,often,sometimes,rarely,ever,never,once,twice,three times,now,just,today,this morning,this month,this year,until now,up to now,so far,in the past a few years,all day,always
现在完成进行体(have/has been＋doing)
We have been livng here for ten years=We have lived here for ten years.
有时不可以与现在完成时互换使用：
Who has been eating my dinner?(还有剩下的）
Who has eaten my dinner?(全吃光了）
现在完成（进行）体和过去时比较
His sister has been an invalid all her life.(她现在还活着)
His sister was an invalid all her life.(已经死了）
过去完成体和过去完成进行体
过去完成体的用法
已完成
表示一个动作或一个状态在过去某时间段以前已完成
未完成
一个动作或状态在过去某个时间之前已开始一直延续到这一过去时间，而且到那时还未结束，仍有继续的可能性
过去完成进行体（had been+ing)
I'd been working for some time when he called
有时和过去完成体可以替换使用
when/before/after/until等连词引导的分句中过去完成体的用法
两个先后发生的事态中可以互换使用
I didn't reached the station until(after)the train had left.
由于连词before和after本身已经体现动作的先后性，所以两个动作都可以用一般过去式
The train (had)left before I reached the station.
也可以在以before引导的时间状语从句中用过去完成体，强调动作未完成或未实现
只有由by the time引导的时间状语从句能同时使用两个过去完成体
By the time I(had)recovered from shock,he had disappeared.
