¿Por qué escuchas al profesor en clase?
This translates to:
Why do you listen to the teacher in class?
Here's a breakdown:
* ¿Por qué? - Why?
* escuchas - you listen (informal "tú" form of the verb "escuchar")
* al profesor - to the teacher
* en clase - in class
The question implies that the listener might be questioning the reason someone would listen to the teacher in class. It could be a rhetorical question, or it could be a genuine inquiry.