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