Concept:Fish and meat are substitutes; a change in the fish market shifts the demand for meat.Explanation:An increase in the supply of fish makes fish cheaper.Consumers then tend to buy more fish instead of meat.As a result, the demand for meat decreases.The supply of meat remains unchanged, so the demand curve for meat shifts leftward.This causes both the equilibrium price and the equilibrium quantity of meat to fall.Answer:A. a fall in equilibrium price and quantity