to speak at the meeting?

题目

to speak at the meeting?
I don't know the professor to speak at the meeting now is from south.
为什么要有一个to呢?
这个事属于哪方面的语法问题啊？不好意思，我没见过to是可以修饰其他成分。
还有，如果没有后面的 is from south 那么这个 to 是否就要省略呢？
是否改为
I don't know the professor who is speaking at the meeting now.
（这个Who 是否正确？）
to可以修饰句子么？我能在语法书的那一部分得到印证？

答案

TO起连接句子的意思,本身是没有什么意思的,用Who是对的,WHO是修饰主语Professor,