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