Which of the following statements about perfect competition and market equilibrium are correct? (A) In perfect competition, firms sell homogeneous products, and the price is determined by market forces. (B) The equilibrium price is the price at which the quantity demanded equals the quantity supplied in a market. (C) In the long run, firms in perfect competition earn supernormal profits due to the entry of new firms. (D) A shift in either the demand or supply curve in a perfectly competitive market results in a new equilibrium price.