Which relation is a function?

A

x -2 -2 0 1 8

y 3 6 0 0 9

B

x -3 4 5 9 12

y 1 -2 -2 0 7

C

x 3 5 7 14 14

y -9 5 -9 1 2

D

x -7 -5 6 8 8

y -3 8 1 1 -9