非谓语动词作状语区别这些状语怎么区别该用不定式还是动名词啊?（还有请顺便再讲一下独立主格是什么,怎么用,通俗一点,谢谢）

一般表示被动,表示动作已完成的,用过去分词.如：
Seen from the top of the hill, the village is too small.
表示主动或者表示动作动作正在进行的,用现在分词.但是如果要强调非谓语动词的动作先于谓语动词发生时,可以用现在分词完成式.如：
Coming into the room, he found his father angry.
Having been hit by the big boy on the nose, the little boy began to cry.
如果用作目的状语或者表示将来的动作就用不定式,但是only+ to do特殊,是作结果状语.如：
I come here only to say good-bye to you.　目的状语
He searched the room only to find nothing. 结果状语

独立主格表示的是所填非谓语动词和句子主语没有任何关系（主谓关系或者动宾关系）,那么久在这个非谓语动词前面加上自己的逻辑主语,这就叫独立主格.如：
The test finished, we began our holiday.
Weather permitting, we are going to visit you tomorrow.

一般表现动作已经完成的，用分词，如：
Having been hit by the big boy on the nose, the little boy began to cry. 已完成
动作虽然不是已经完成，但也并不是表将来的。以及一般现在时的，如：
Coming into the room, he found his father angry. 不表将来
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