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