现在分词和过去分词作状语的主要区别在于：现在分词与修饰的主语为主动关系，过去分词与修饰的主语是被动的关系。
（1）现在分词作状语时，现在分词的动作就是句子主语的动作。
He went out shutting the door behind him.
Not knowing what to do, he went to his parents for help.
（2）过去分词作状语时，过去分词所表示的动作和句子的主语承受的动作，它们之间的关系是被动关系。
Given more attention, the trees could have grown better.
Faced with difficulties, we must try to overcome them.
