Which set of ordered pairs represents a function?
{(-3,1), (8, -2), (0,0), (8,6)}
{(-1,-8),(-8, –3), (-8,-7), (4,1)}
{(-3,-8),(-3,-7), (2,-7), (6,-4)}
{(1,-1),(-3,-8), (8, -1),(0,5)}