Which of the following sets of ordered pairs are not a function?


A.(2,1), (3,4), (5,6), (2,7)


B.(3,1), (−3,1), (0,0), (5,1)


C.(1,1), (2,2), (3,3), (4,4)


D.(4,1), (6,7), (8,9), (4,7)


(2,4), (2,5), (2,6), (2,8)