Which one is not a assumption of the theory of demand based on analysis of indifference curves?

Q.        Which one is not a assumption of the theory of demand based on analysis of indifference curves?

A.           Given scale of preferences as between different combinations of two goods   

B.            Diminishing marginal rate of substitution

C.            Constant marginal utility of money             

D.           Consumers would always prefer more of a particular good to less of it, other things remaining the same

Answer: Constant marginal utility of money