Which relation is a function?
O A.
{(5,2), (-2,-8), (7, -1) (-2, 6)}
B.
{(7, 1), (4,2), (4,-4), (7,3)}
C.
{(6,5), (3, 2), (6,4), (5,8)}
O D.
{(6,-4), (5, 8), (3,6), (-4,-4)}