Question

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？

Answer 1

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,

Answer 2

I don't know the professor to speak at the meeting now is from south.
我不知道现在在会上讲话的教师是从南方来的。

to speak at the meeting now 是修饰professor.

因为
I don't know the professor is from south. 这是主句。

Answer 3

没有to读不通的 看看书上应该有
Who应该正确