10. Which relation is a function?
la A (8, -4), (8, 4), (6, -3), (6, 3).
(0,0)
B (4,7), (8,5), (6,4), (5, 3), (4, 2)
C (0,0), (1, 1), (2, 2), (3, 3), (4,7)
D (0,0), (1,0), (1, 1), (2, 1), (1, 2)