Which function has an inverse that is also a function?
{(-1, -2), (0, 4), (1,3), (5, 14), (7,4)}
{(-1,2), (0,4), (1,5), (5, 4), (7, 2)}
{(-1,3), (0.4), (1, 14), (5, 6), (7, 2)}
{(-1,4), (0.4), (1, 2), (5,3), (7, 1)}