进行体表示长动作该如何应用？

所谓“进行体”是英语语法名词 English progressive aspect 的中文翻译，其语法分析意义在于解释谓语动词进行时态以外的“动词+ing”用法与语义表达，即非谓语动词的使用和词义。

进行体：

一个长动作作为背景，被一个短动作打断，长动作往往用进行体，短动作用一般体。如：

My brother fell while he was riding his bicycle and hurt himself．

我弟弟骑自行车时从车子上掉了下来，伤了自己。

The students were writing busily when Miss Brown went to get a book she had left in the office．

同学们在忙着写作，这时布朗老师去取她忘在办公室的书。

Tom slipped into the house when no one was looking．

当没人注意的时候，汤姆溜进了房子。

The reporter said that the UFO was traveling east to west when he saw it．

那位记者说，当他看到那个不明飞行物时，它正在自东向西飞行。