Which set of ordered pairs represents a
function?
{(6, -7), (6, 7), (5,9), (0, -7)}
{(-8, -3), (4, −9), (−5, 7), (8, −3)}
{(3, 8), (4,-5), (4, -1), (-4, 6)}
{(-3,5), (-3, 6), (3,-1), (8,4)}