问题 答案里说It充当形式主语，我不太明白

句子是这样的：It worries me the way he keeps changing his mind.

问题 have的问题

This tooth is too bad to be filled anymore.It has to be pulled.Do you agree to have it extracted? 这里的have it extracted .  have是动词 it 是宾语 extracted是补语修饰it 对么？可是这样的话我感觉have没有放在这里的意义，直接把extracted 变成动词放在it前面...

话题 Don’t mention it

话题 belieive it or not

话题 as it had with

话题 with its own standards

话题 it is no good

话题 as we know it

话题 Were it not for...

话题 it is time that...

话题 So this is it

话题 it looks as if...

话题 be it在文中的意思

话题 it作形式主语，不定式

话题 it is fun doing