According to your textbook, if you quoted steven covey, a professor at brigham young university and author of the seven habits of highly effective people, on the principles of effective time management, what kind of testimony would you be using?

I believe the answer is: Expert testimony.
Expert testimony refers to the type of testimony that given by professionals whose career revolves around a relevant field as our topic.
In this particular case experts could include academic professors, economists, or experienced professors.

Sector is best defined as (part).