Which set of ordered pairs represents y as a function of x?
F {(−9, 2), (0, 6), (1, −2), (−3, 6)}
G {(−1, 0), (4, 3), (−7, −3), (−1, −8)}
H {(3, 2), (−4, −2), (3, 1), (−4, 1)}
J {(5, 4), (2, 3), (1, 1), (2, 4)}