Which set of ordered pairs represents y as a function of x?
O {(4,7), (4,6), (4,4), (4,1)}
{(3, 2), (4,3), (5,2), (2.6)}
o {(2,5), (3, 1), (2, 1), (4,7)
o {(1,3), (3,5), (2,5), (1.6)]