In which set of ordered pairs is y a function of x?

(-4, 2), (-3, 1), (-1, 0), (-1, 1)

(-1, 1), (-2, 2), (-1, 3), (0, 4)

(4, 4), (2, 3), (3, 2), (4, 1)

(1,1) (2, 1), （3. 3), (4,4)