In which set of ordered pairs is y a function of x?
A.{(3, 2), (3, 5), (3, 7)}
B.{(+1, 3), (0, 2), (1, 3)}
C.{(0, 1), (1, 2), (1,3)}
D.{(-2, 0), (0, 2), (2, 2)}