Which ordered pairs cause this relation NOT to be a function? Why?

{(0, 0.5), (0.5, 1), (3, 1), (1, 6), (3, 2)}

A) (0.5, 1) and (0, 0.5); A function cannot contain decimals.
B) (0.5, 1), (3, 1); The same y-value has different x-values.
C) (3, 1) and (3, 2); The same x-value has different y-values.
D) (3, 1) and (3, 2); The x-value in a function cannot be greater than the y-value.