key to the door短语中为什么用to?可以用of么?如果可以,它们两个有什么区别么?

问题描述:

key to the door短语中为什么用to?可以用of么?如果可以,它们两个有什么区别么?

不能用of.key to the door 是固定搭配,必须用to,类似的用法还有:
the answer/solution/way/entrance to .
如:Do you know the answer to the question
We had a solution to the problem .
This is the entrance to the park .