Complementary goods relate to each other as substitutes relate to: A: demand changes :: B: price changes :: C: quantity supplied changes :: D: market equilibrium changes

Complementary goods are products that are usually consumed together, like peanut butter and jelly. When the price of one complementary good goes down, the demand for the other often increases because people tend to buy both together. In contrast, substitute goods are products that can replace each other, such as butter and margarine. When the price of one substitute good goes up, the demand for the other typically increases as people switch to the cheaper option. Therefore, the correct answer is that complementary goods relate to each other as substitutes relate to demand changes, because both relationships show how price changes can influence the amount people want to buy.