Question

Which set of ordered pairs represents a function?

a
{(1, 8), (8, 1), (1, 5), (5, 1)}
{(2, 1), (3, 1), (4, 3), (5,3)}
{(5, 1), (3, 8), (3, 7), (7, 1)}
{(5, 1), (5, 6), (1,3), (9, 7)}

Answer 1

Second option, since there are no x repeats.