PLEASE HELP!!
Which relation is a function?
A. {(4, 0), (4, -5), (4, -2), (2, -4)}
B. {(0, 1), (1, -4), (0, 5), (1, -7)}
C. {(3, 4), (1, -2), (-5, 4), (2, 2)}
D. {(3, -1), (2, 3), (10, 2), (10, 8)}