Price elasticity of demand measures: a. how consumers change their purchases of a good in response to a change in income. b. how consumers change their purchases of a good in response to a change in the price of a substitute good. c. the change in price brought about by a change in consumer demand. d. how consumers change their purchases of a good in response to a change in its price. a

The correct answer is: **d. how consumers change their purchases of a good in response to a change in its price.** ### Explanation: Price elasticity of demand specifically measures the responsiveness of the quantity demanded of a good to a change in its price. It quantifies how much the quantity demanded will increase or decrease when the price of the good changes. - **Option a** refers to income elasticity of demand, which measures how demand changes in response to changes in consumer income. - **Option b** relates to cross-price elasticity of demand, which measures how the quantity demanded of one good changes in response to a change in the price of a substitute or complementary good. - **Option c** does not accurately describe price elasticity of demand; it refers more to the concept of supply and demand equilibrium. Thus, option d is the most accurate definition of price elasticity of demand.