Question

现在分词作原因状语和作伴随状语怎么区分最好有例句

Answer 1

Knowing he was on the way, she was happy.
分词原因状语一般是状态动词，位于句子前部。可改为原因状语从句：
Because she knew he was on the way, she was very happy.
The boy sat in the room, reading a book.
分词伴随状语一般表示次要动词，位于句子后部。可加and还原成为并列谓语：
The boy sat in the room and read a book.

Answer 2

现在分词作原因状语就是现在分词在句子中的成分是状语,表示原因的状语.
通常情况是省略for或者省略其它表示原因的词.如Being ill,I had to stay at home
做伴随状语就是表示和谓语动词几乎同时伴随发生的动作,如He stood there,singing loudly.