Select Is a Function or Is not a Function to correctly classify each relation. Title [Is a Function] [Is not a Function]

A: {(3, 2),(6, 4),(9, 6),(12, 8)}

B: {(2, 3),(2, 5),(3, 6),(9, 4)}

C: {(2, 4),(6, 3),(4, 8),(6, 6)}

D: {(3, 4),(5, 2),(6, 8),(6, 4)}

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm