Which of the following sets of ordered pairs represents a function?
OA. {(9,7), (0, -4), (8,4), (0,6) }
OB. {(0, 1), (0, -1), (2, 4), (5,6) }
OC. {(1, 8), (1, 0), (1, -8), (1, 1) }
OD. {(2,4), (0, 0), (4,8), (3,6)}