1 一般过去时用来谈论过去开始和结束的活动。过去进行时用来谈论过去正在进行或者发生的活动。
Why were you at office so later yesterday?
I was working.
2 过去进行时有三种用法
①表明过去某一特定时间内某个动作正在进行
What project was Carol working on last month?
She was working on the McFierson project with Luis Ramirez.
②表明过去某个动作正在进行中，又发生了另外一动作(并且可能打断第一个动作)
Luis was finishing the report when Carol called.
③表明过去两个动作正在同时发生
While Carol was takling on the phone, Luis was reading the report.
3 对于一些动词live, work, study 一般过去时和过去进行时用法相同
She was working(worked) on the McFierson project with Luis Ramirez.