Which relation is a function?


{(5, 0), (0, 1), (5, 2), (4,4)}

{(0, 1), (−4, 1), (4, 2), (−4,−1)}

{(1, 2), (2,4), (−1, 2), (0,3)}

{(3, 2), (2,1), (−1, 2), (3,3)}