Which of the relations given by the following sets of ordered pairs is a function?
O {(1,2), (-4, 8), (-3, 5), (1, - 2), (7, 12)}
O {(5, 4), (4,3), (3, 2), (4, 5), (2, 1)}
O {(6, 1), (3, 1), (3, 5), (2, 4), ( − 1, 2)}
O {(5, 4), (5, 6), (5, 8), (5, 10), (5, 12)}