Which set of ordered pairs (x, y) could represent a linear function?
A = {(3,5), (5,1), (7, -2), (9,-6)}
B = {(2,-5), (5,1), (6,3), (7,6)}
C = {(-4,3), (-2,0), (0, -4), (2, –7)}
D = {(-3,7), (-1,5), (1,3), (3, 1)}