Choice "B" is correct. The demand curve illustrates the maximum quantity of a specific good that consumers are willing and able to purchase at each and every price, all else being equal. Thus, the demand curve reflects the impact that price has on the amount of a product purchased.Choice "a" is incorrect. The supply curve, not the demand curve, measures the maximum quantity of a specific good that sellers are willing and able to produce at each and every price.Choice "c" is incorrect. The movement of points along the supply curve, not the demand curve, represents a change in quantity supplied as a result of a change in price and is the measure of a willingness of producers to offer a product at alternative prices.Choice "d" is incorrect. Cross elasticity, not the demand curve, measures the impact that price has on the purchased amount of two related goods (either substitute or compliment).