user: Who is the greatest NFL running back of all time?

assistant: Arguably, Barry Sanders is the greatest running back of all time.  Unlike Emmitt Smith, Barry Sanders played behind an offensive line that was soft and weak.  There were no pro bowl players on the Detroit Lions offensive line during Barry's tenure in Detroit.  Barry Sanders also retired at his peak because he was disheartened by the direction of the franchise's inability to improve year over year.

user: According to the passage what is the best way of making progress with mathematics?

assistant: Working through the more difficult mathematical books with great diligence, collect questions and difficulties and seek help from a professor to solve them

user: Classify these as a synthetic or natural fiber

assistant: wool, polyester, cotton, silk, nylon, aramid, jute