When the price of x rises， Marvin responds by changing his demand for x.The substitution effect is the part of this change that represents his change in deman

D.

A.holding the prices of substitutes constant.

B.if he is allowed to substitute as much x for y as he wishes.

C.if his money income is held constant when the price of x changes.

D.none of the above.

正确答案：none of the above.