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