Which of the following lists of ordered pairs is a function?



(-1, 2), (2, 3), (3, 1), (2, 5)



(1, 2), (4, 0), (3, 5), (4, 3)



(2, 5), (3, 6), (6, 9)



(2, 5), (3, 6), (2, 1)