For the each k Z, define Mk(small k under)= {kx: x = Z}. Let f ={(4x,6x):xEZ). Consider the following propositions. (I) The relation f is a function M4M6. (II) The relation f-1 is a function M6 M4. Which of the following is true? A. (I) and (II) are both true. B. (I) is true, but (II) is false. C. (II) is true, but (I) is false. D. (I) and (II) are both false.