When he was in Beijing,he visited places where he had played as a child.
当他在北京时，他参观了他小时候早就玩过的地方。
It took me a long time before I was able to fully appreciate what they had done for me.
我花了很长时间才充分理解他们之前为我做的一切。
在过去的某个时间或动作以前已经发生的动作或已经存在的状态
We hadn't met each other since we left Japan last time.
自从我们上次离开日本后，就没有见过面。
从过去的某一时间开始，一直延续到过去另一时间的动作或状态。
I had hoped to send Peter a gift ,but I couldn't manage it.
我希望给彼得送一份礼物，但始终没做到。
未曾实现的想法，还有suppose,expect,intened,mean
I'd(would) rather you hadn't been present. 我宁愿你不在场
I wish we had never met each other.
我希望我们从未遇见过。
If only we had listened to their adviced.
如果我们听从他们的建议就好了
The game had hardly begun when it started raining.比赛才刚开始，就下雨了
Hardly had I opened the door when he told me that. 他告诉我，我几乎没有开门
He had no sooner bought the car than he sold it. 他刚完车就卖了
It was the second time he had been out with her. 这是他第二次和她出去了
