Which set of ordered pairs represents a function?
{(9,4),(-1,2), (-3,3),(-1,-6)}
{(-7,4), (7,2), (1,2), (-4,-4)}
{(-8,4), (–8,1), (0, -1), (5, -6)}
{(–9,–8), (2,-4), (–9,8), (0, –4)}


Someone Please help ASAP