关于代词指代不明

问题描述:

关于代词指代不明
There's one thing i don't know why.
It doesn't even matter how hard you try.
这句话里面的it指的是什么?
如果是one thing的话
就是one thing doesn't even matter
非常的不通顺啊?
而it只能是代词指代别的东西啊?
应该说it指代是什么东西呢?
放回去也能通顺的呢?

it是形式主语.真正的主语是how hard you try.这句话还可以改成:
how hard you try doesn't even matter.