Which relation is a function?

A.
{–2, 10), (–6, 10), (–2, 3)}

B.
{(0, 3), (0, 9), (12, –4)}

C.
{(5, 5), (5, 9), (5, 15)}

D.
{(–5, 1), (4, 9), (6, 10)}