In which set of points is y a function of x? A. {(1, -2), (0, 1), (1, 1), (1, 2)} B.{(1, 2), (0, 1), (1, 2), (1, 1)} C.{(2, 1), (0, 1), (1, 0), (2, 1)} D.{2, 2), (1, 1), (0, 1), (-1, -1)}