时间、原因等状语从句可以转换成分词作状语，但这种转换是有条件的，也可以總结出一些规律。
一、基本规则，也是最重要的规则：从句的主语与主句的主语必须一致，从句变成分词作状语，而主句不变。如：
1. They did not go to the party because they had a lot of
work to do.
此句
because
引导原因状语从句，由于从句的主语与主句的主语都是
they
，可以把从句中的
because
和
they
去掉，把
had
变成
having
，即成现在分词短语作原因状语：
Having a lot of work to do, they did not go to the
party.
2. When ice is heated, it will be changed into
water.
此句
when
引导时间状语从句，由于从句的主语与主句的主语都是
ice,
可以把从句中的主语和
be
动词去掉，或者连词
when
也可以去掉，改成过去分词
heated
作状语。
When heated, ice will be changed into water.
或者
Heated, ice will be changed into water.
二、从句的主语如果与主句的主语之间逻辑上是主谓关系，动作为正在进行或完成，则转换成现在分词
;
如果是被动关系，则转换成过去分词。
1. When he heard a cry for help
，
he rushed out.
从句中，
he
与
hear
是主动关系，表示
“
他听见
”
，可变成现在分词作时间状语，或者保留连词。
Hearing a cry for help
，
he rushed out.
When hearing a cry for help, he rushed out.
2. After the girl learned some simple Chinese, she was able
to communicate with us.
after
引导原因状语从句，从句主语与主句主语一致，
learn some simple Chinese
与
be able to communicate with us
之间有先后顺序，则句子可以转换为：
After learning some simple Chinese, she was able to
communicate with us.
（用
after
表示动作先后）
或
Having learned some simple Chinese, she was able to
communicate with us.
（用
having done
表示动作先后）
3. Because he hadn’t finished his homework, he didn’t watch
the football match.
because
引导原因状语从句，从句主语与主句主语一致，用现在分词表示主动，但从句的动作在主句动作之前，分词要用完成式，则句子可以转化为：
Not having finished his homework, he didn’t watch the
football match.
（注意：
not
放在分词的前面）
4. When he was asked by the teacher, he answered
politely.
when
引导的从句中，
he
和
ask
是被动关系，则变成过去分词作时间状语，或保留连词。
Asked by the teacher, he answered politely.
或
When asked by the teacher, he answered politely.
5. When the tall building was attacked by terrorists, the
tall building collapsed.
when
引导时间状语从句，从句主语与主句主语一致。根据句意
;
大楼因为受到恐怖分子的袭击而倒塌，从句动作先于主语动作，则句子可转换为：
Having been attacked by terrorists, the tall building
collapsed.
三、如果从句的主语与主句的主语不一致，该怎么办？请看下例：
1. As the heroes deeds moved them deeply
，
they decided to study even harder.
句中，主句的主语是
they
，而从句主语是
the heroes deeds
，主语不一致，这时可以把从句变换一下句型，变成被动语态。即：
As they were deeply moved by the
heroes deeds.
从句的主语与主句的主语都是
they
，就可转换成：
Deeply moved by the heroes deeds
，
they decided to study even harder.
2. The professor came into the lab; a group of students
followed him.
这是两个简单句，如果中间加个
and
也可看成并列句。因为主语不同，可以先把第二句变成：
He was followed by a group of students.
全句就可转换成：
Followed by a group of students
，
the professor came into the lab.
四、獨立主格结构
分词作状语时逻辑主语与主句主语应保持一致，但当分词逻辑主语与主语不一致时，分词要有自己独立的逻辑主语，这种主语常常是名词或代词，置于动词
-ing
形式或动词
-ed
形式之前。这种
“
名词
/
代词
+
动词
-ing/
动词
-ed”
结构在语法上被称为独立主格结构。此时分词形式的选择取决于名词
/
代词与
v-ing / v-ed
形式所表示动作的逻辑关系，如果它们之间表示主动或分词动作正在进行，选择现在分词，如果它们之间表示被动或完成，选择过去分词。
1. When spring came, the trees turned green.
可把状语从句转变成名词
+ v-ing
。
Spring coming, the trees turned green.
2. Because the question was settled, they felt
released.
可把原因状语从句转变为名词
+ v-ed
的独立主格结构：
The question settled, they felt released.
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