Which set of ordered pairs does not represent a function?
{(3,-5), (-3,-5),(-6,2), (-4,6)}
{(0, -1), (7,-6), (6, -5), (9,-6)}
{(-1,7), (-6, -9), (-5,8), (-1,9)}
{(-2,-2), (3, -8), (-9, -8), (-3,2)}