Which set of ordered pairs does not represent a function?

Group of answer choices

{(6, 0), (-9, 5), (1, -5), (0, 0)}

{(4, 6), (6, 8), (3, 2), (-6, 8)}

{(-9, -7), (-8, -7), (8, 2), (9, -5)}

{(-8, 6), (-8, 5), (-9, 4), (-5, 3)}