同学你好，该知识点来自沪江网校《新概念英语1、2、3、4册连读【限时特惠班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
I joined them是一个过去事件，work是发生在joined之前的，是过去的过去，而且动作是持续的，所以是过去完成进行时had been doing
而have worked是现在完成时，不能表示过去的过去。


一、结构形式

过去完成进行时由“had been+现在分词”构成，因此无人称变化。

二、用法归纳

1.过去完成进行时表示持续到过去某时的一个动作(可算是现在完成进行时的过去式)：

The ground was wet. It had been raining. 地是湿的。此前一直在下雨。

At last the bus came. I had been waiting for half an hour. 最后公共汽车来了，我已等了半小时。

She was out of breath. She had been running. 她气喘吁吁，她一直在跑来着。

2.过去时间可用一个时间状语表示：

When I first met her, she had been working in the company for ten years. 我第一次见到她时，她在那家公司已工作十年了。

I had not been waiting long when a taxi drew up. 我没等多久就来了一辆出租车。

Until/Up till then she had been living with her daughter. 到那时为止她一直和她女儿一起住。

3.但在更多情况下过去时间由另一句子表示出来，无需加上时间状语：

Her eyes were red. It was obvious she had been crying. 她眼睛红红的，显然她是哭了。

Jane was annoyed. Peter had been phoning her every night. 简很不高兴。彼得一直每晚给打电话。

4.有时上下文可说明是谈过去的事，因此不需要时间状语：

She had been watching TV all day. 她看了一天的电视。

I had been reading your book. 我一直在看你写的书。

5.这个时态也可用在某些从句中，这时从句的动作发生在主句的动作之前而对其有影响：

I heard you’d been looking for me. 我听说你一直在找我。

That was just the letter I had been expecting. 这正是我一直期待的信。

That was exactly what we had been trying to do. 这正是我们一直想做的事。


祝同学学习进步~