Which set of ordered pairs does not represent a function?
{(−5, −7), (−1, 4), (−3, 4), (5, 2)}
{(-8, -7), (4, 7), (4, −9), (5, -6)}
{(−5, −7), (−6, 7), (−1, −9), (9, 7)}
{(4, 5), (1, 5), (3, −7), (7, 6)}