Help me please
Which of the following relations is a function?

A.

(3, 4), (-4, 6), (3, 3), (-8, 2)


B.

(3, 0), (-4, 3), (8, 1), (-4, 5)


C.

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


D.

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