现在完成时:already,yet,now,just,by this time,today,this morning,this week,recently,lately,since then,often,(ever)since,before,ever
过去完成时常用于以下固定句型:
1)hardly, scarcely, barely + 过去完成时+ when + 过去时.例如:
Hardly had I got on the bus when it started to move.
2)no sooner +过去完成时+ than +过去时.例如:
No sooner had I gone out than he came to see me.
3)by (the end of ) +过去时间,主句中谓语动词用过去完成时.例如:
The experiment had been finished by 4 o’clock yesterday afternoon
2) 表示过去某时间前已经发生的动作或情况,这个过去的时间可以用by,before等介词短语或一个时间状语从句来表示;或者表示一个动作在另一个过去动作之前已经完成
简单点 判断过去完成时, 就是比较前后2个句子,都发生在过去,那就是过去的过去,就是过去完成时