5．以when，while引导的时间状语从句和以if引导的条件状语从句，如果从句主语和主句主语一致时，可简化为现在分词状语，表示谓语动作发生在该状语动作的进行过程之中。
例如：
When he turned on the radio，he found it broken．(简化前)
When turning on the radio，he found it broken．(简化后)
While she was walking along the street，she was hit by a car．(简化前)
While walking along the street，she was hit by acar．(简化后)
6．原因状语从句的主语与主句主语一致时，可简化为分词短语作状语。例如：
Since l didn't know Chinese，I tried to speak to her in English．(简化前)
Not knowing Chinese，I tried to speak to her in English．(简化后)
要注意的是，形容词短语也可用作表示原因的状语，用以代替原因状语从句，放在句首、句末均可，但一般应加逗号。例如：
As he was thirsty and eager to get a little rest，he went into the tea-house．(简化前)
Thirsty and eager to get a little rest，he went into the tea-house．(简化后)
7．在时间、原因、条件等状语从句中，若从句和主句主语不一致时，可简化为分词复合结构作状语。有时也可简化为“with/without名词或代词十分词(短语)”形式作状语。例如：
When the film start appeared, the children got exited．(简化前)
The film start appearing，the children got exited．(简化后)
If all the work is done, you can have a rest．(简化前)
With all the work done，you can have a rest．(简化后)
Nothing can live if there is no air．(简化前)
Nothing can live without air．(简化后)
8．让步状语从句的主语与主句主语一致时，可简化为分词短语。
作状语；不一致时，常简化为with或in spite of介词短语作状语。例如：
Although he faced his death，he didn't say anything before the enemy．(简化前)
Facing the death，he didn't say anything before the enemy. (简化后)
Although there was danger，he rushed out to carry the boy to safety．(简化前)
In spite of danger，he rushed out to carry the boy to safety．(简化后)