Which of the following tables represent a function?

A.
X 3 3 4 4
Y 2 -2 3 -3

B.
X 5 -5 5 -5
Y 2 2 8 8

C.
3 3 5 5
Y 4 5 6 7

D.
X 4 -4 5 -5
Y 2 2 3 3