Which relation is not a function?
A
{(10,−5),(8,−4),(4,−2),(2,0)}

B
{(1,−2),(1,−4),(1,0),(1,8)}

C
{(−3,9),(−2,4),(−1,1),(1,1)}

D
{(3,10),(5,−5),(6,6),(9,11)}