which pairs are a linear function? a. (-4,8) (-1,2) (1,2) (2,4) (3,6) b. (-6,-16) (-2,-8) (0,-4) (1,-2) (3,2) c. (0,-2) (1,0) (2,2) (3,7) (4,14) d. (-2,-7) (-1,0) (0,1) (1,2) (2,9)