Which of the following relations is not a function?

(2, 4), (-2, 2), (2, 1), (-8, 2)


(-8, 4), (2, 3), (-2, 1), (5, 2)


(5, 4), (-2, 2), (2, 1), (-8, 2)


(-2, 4), (2, 2), (5, 1), (-8, 5)