Which of the following relations describes a function? A. { (0, 3), (1, 4), (2, 1), (2, 5) } B. { (0, 3), (1, 4), (4, 5), (9, 6) } C. { (0, 3), (1, 4), (1, 2), (4, 5) } D. { (-4, 5), (-1, 2), (-1, 4), (0, 3) }