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