Which of the following is discontinuous at x=9?

• A. ( frac{x^2-81}{x-9} )
• B. ( frac{x^3-20x^2+117x-162}{x-9} )
• C. ( frac{x^2-11x+18}{x(x-9)} )
• D. ( frac{x^2-13x-90}{x-9} )