A.
demand curve for airline tickets downward, decreasing the price received by sellers of airline tickets and causing the quantity of airline tickets to increase.
B.
demand curve for airline tickets downward, decreasing the price received by sellers of airline tickets and causing the quantity of airline tickets to decrease.
C.
supply curve for airline tickets upward, decreasing the effective price paid by buyers of airline tickets and causing the quantity of airline tickets to increase.
D.
supply curve for airline tickets upward, increasing the effective price paid by buyers of airline tickets and causing the quantity of airline tickets to decrease.