Mark the relations that ARE functions
{(2,5) (-3, 4) (0,1)}
{(1,1) (2,1) (0, 1) (-8, 1)}
{(3, -2) (9, 1) (3, 5) (9, 3)}
{( 2,5) (0, 3) (-1, 1) (7, 13)}