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