The Past Indefinite and Past Continuous Tense 一般过去时和过去进行时
1. 一般过去时表示在确定的过去时间里所发生的动作或存在的状态，也可表示在过去一段时间内，经常性或习惯性的动作。When I was a child, I often played football in the street.
2. 过去进行时表示过去某时正在进行的状态或动作。过去进行时的主要用法是描述一件事发生的背景；一个长动作发生的时候，另一个短动作发生。As he was reading the newspaper, Granny fell asleep在他看报纸时，奶奶睡着了。
3. 应特别注意两个时态的区别：They watched the train until it disappeared. (一般过去时表示watch动作已结束) She was writing a book about China last year but I dont know whether she has finished it. 过去进行时不表示write动作已结束) I dont think Jim saw me; he was just staring into space. (过去进行时表示过去某时正在进行的状态或动作)