The substitution effect of a price change refers to A. the movement along the demand curve due to a change in purchasing power brought about by the price change. B. the shift in the demand curve due to a change in purchasing power brought about by the price change. C. the shift of a demand curve when the price of a substitute good changes. D. the change in quantity demanded that results from a change in price making a good more or less expensive relative to other goods that are substitutes.