I happen to know the answer to your question.the answer to your question.to可以换成of 或者 for 还是说,这是一个习惯用法,所以不能换?

I happen to know the answer to your question.the answer to your question.to可以换成of 或者 for 还是说,这是一个习惯用法,所以不能换?
I happen to know the answer to your question.
the answer to your question.
to可以换成of 或者 for
还是说,这是一个习惯用法,所以不能换?

I happen to know the answer to your question.the answer to your question.to可以换成of 或者 for 还是说,这是一个习惯用法,所以不能换?
没错.
的确是习惯用语．
其他的还有比如
the road to
the key to
你是有心人啊

answer to 是固定搭配，（表答案时）。
有时用answer for, 意义偏于“满意的”。