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