Which set of ordered pairs represents a function?
{(-4,9), (-4, 7), (1, -5), (7, —8)} {(-5, -5), (–9,1), (8, -6), (-9, -4)}
{(-6, -6), (-2, -2), (7,-6), (-5,0)}
{(-7, -9), (-7, -7), (3, –7), (5, -5)}