Which of the following statements is true?

A. A price floor is a minimum price and must be set above the equilibrium price to be effective.

B. A price floor that is effective results in excess demand.

C. A price ceiling is a maximum price that must be set above the equilibrium price to be effective.

D. A price ceiling is a minimum price that must be set below the equilibrium price to be effective.

E. A price ceiling is a minimum price that must be set equal the equilibrium price to be effective.