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