Which set of ordered pairs is a function?
{(-21).(-4, 2), (0, 3), (4,1),(-2,5)}
{(-1,5), (-1,4),(-1,3), (-1,2), (-1,1)}
{(-6, -4), (-4,-2), (0,0).(-4, 2). (-6,4)}
{(-5,1). (-3, 2), (-1,3), (1,4), (3,5)}