3.表示动作发生的背景

(1)在口语和记叙文中，常用过去进行时所表示的持续性动作提供背景，以此引出一般过去时所表示的新动作。

The day was fine．People were hurrying to work or to school，cars were moving in all directions like spiders weaving a web．Among the mwas a girl who was waiting for the bus，reading a morning newspaper．A boy came to her．

天气很好。人们行色匆匆，有的赶着去上班，有的赶着去上学。车辆朝着各种方向行驶，就像是蜘蛛在编织一张网一样。这中间有一个姑娘，她在等公汽，看着当天的晨报。一个男孩朝她走了过来。

I couldn't believe my eyes!The car was upside down and the driver was bleedingand screaming．(人教大纲版高二上第59页)

我简直无法相信自己的眼睛!车翻了，驾驶员在流血，在喊叫。

(2)过去进行时表示的动作，即背景动作或状况的延续性较长，主要动作较短，并且往往发生在背景动作进行之中。此时，主要动作通常用一般过去时，另一动作通常用具有并列含义的when，as，while引导的从句形式表达。

Toms lipped into the house when no one was looking．

当没有人注意时，汤姆溜进了房子。

Rick fell and hurt while he was riding his bicycle．

当里克骑自行车时，从车上掉下来受伤了。

Just as I was opening the door，Mr．Zhang came back．

我正要开门时，张先生来了。

I went on shouting at him while everyone was looking at him．(人教大纲版高一下第55页)

在众目睽睽下，我继续对他吆喝。

有时，如果主要动作和背景动作都是延续性的或同时发生的，那么主句的动词和从句的动词都可用过去进行时。

While he was waiting for the bus，he was reading a newspaper．

当他等车的时候，他在看报纸。(两个动作都是延续的)

My wife was cooking the dinner while I was working in the garden．

我妻子做饭，我收拾花园。(两个动作同时进行)

(3)当这种过去进行时后接一个when引导的从句时，常常表示意外。

A few days later，I was moving forward over a slope that seemed safe when suddenly without warning my world dropped out from under my skis．(人教大纲版高一下第31页)

几天以后，我正在一个似乎安全的斜坡上往前进，突然，滑雪板下的大地毫无预兆地陷下去了。

I was wandering through the street when I caught sight of a tailor's shop．

我正在街上溜达时看到了一家服装店。