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