Which of the following sets of ordered pairs represents a relation that is not a function?
A) (1,1), (2,3), (6,11), (10,19), (50,99)

B) (-5,-2), (-4,-1), (1,4), (2,5), (3,4)

C) (1,3), (3,9), (5,15), (7,21), (11,33)

D)(2,4), (8,10), (8,16), (11,13), (15,17)