The question is difficult to answer. 这个问题很难回答。的“TO”是什么意思？

to 没意思。 是助词结构中需要的

be difficult to do something是短语

应该是:The question is too difficult to answer.
too...to是个词组

都说是动词不定式拉
楼主你不厚道啊,关闭之前那个同样的问题,太XX了吧

to没有含义，
原句是
To answer the question is difficult.

但是说 answer the question is difficult是不符合语法的。

动宾短语做主语必须加个to在前面。
呵呵！