Identify the relation that is also a function.
A. {(5, 4) (5, 1) (5, 3) (0,5)}
B. {(4, 2) (4, -3) (9, 3) (9,-3)}
C. {(1, 0) (2, 3) (3, -1) (1,5)}
D. {(0, -1) (1, -2) (2, -3) (-1, 2)}