Which of the following is true?

a. The intersection of the supply and demand curves shows the equilibrium price and equilibrium quantity in a market.

b. A surplus is a situation where quantity supplied exceeds quantity demanded.

c. A shortage is a situation where quantity demanded exceeds quantity supplied.

d. Shortages and surpluses set in motion actions by many buyers and sellers that will move the market toward the equilibrium price and quantity unless otherwise prevented.

e. All of these are true.