Correct Option: A

Price elasticity of demand is a measure of responsiveness of the quantity of a good or service demanded to changes in its price. This measure of elasticity is sometimes referred to as the own-price elasticity of demand for a good, i.e., the elasticity of demand with respect to the good's own price, in order to distinguish it from the elasticity of demand for that good with respect to the change in the price of some other good, i.e., a complementary or substitute good.