Which of the following relations is not a function?
A) (-7,4)
(4,3)
(-5, 1)
(6,2)

B) (-5,4)
(4,2)
(6,1)
(-7,5)

C) (6,4)
(-5,2)
(4,1)
(-7,2)

D (4,4)
(-5,2)
(4,1)
(-7,2)