1.现在分词常可用作状语，表示：
1)同时发生的另一动作(多为伴随的动作)：
Mr.Brown sat in a boat fishing.
布朗先生坐在一条船上钓鱼。
Some left the hall still weeping.
有些人离开大厅时还在哭泣。
Following Tom，they started to climb.
他们跟着汤姆开始往上爬。
2)原因：
Not knowing her address(=As we don't...)，we couldn't get in touch with her.
由于不知道她的地址，我们没法和她联系。
Many of us，being so excited，could not go to sleep.
我们很多人是那样激动，没法睡着。
Having already seen the film twice(=As she had already seen...)，she didn't want to see it.
这电影她己看过两遍，不想再看了。
3)时间：
Turning around(=As he turned around)，he saw an ambulance driving up.
他转过身看到一辆救护车开了过来。
Hearing the news(=When they heard...)，they all jumped with joy.
听到这消息他们都高兴得跳起来了。
Having finished her work(When she had finished...)，she started to read the newspaper.
她干完工作，开始看报。
2.有时现在分词短语可由when或while引起：
Be careful when you are crossing the street.
过街要小心。
I got engaged to her when traveling last winter.
去年冬天旅游时我和她订了婚。
Don't mention this while (you are)talking to him.
和他谈话时别提此事。
While doing so he hurt his leg.
这样做使他腿受了伤。
3.一般说来，现在分词表示的是句子主语的动作，这从上面句子中可以看出。但在下面这类句子中，现在分词表示说话人的态度，可以不表示主语的动作：
Supposing we lose what shall we do?
假定我们输了怎么办?
It has cost，roughly speaking，$500.
这事大致花了500美金。
