an industry is populated by identical firms, facing constant input prices and having all the other characteristics of a perfectly competitive market....

an industry is populated by identical firms, facing constant input prices and having all the other characteristics of a perfectly competitive market. which of the following statements describes the new long-run market equilibrium resulting from a shift in demand?

A. shift in demand has no effect on long run average cost and there is no change in equilibrium price and quantity. 

B. shift in demand changes equilibrium price and quantity.

C. shift in demand has no effect on long run average costs resulting in a change in equilibrium quantity not price.

D. shift in demand has no effect on long run average cost resulting in change in equilibrium price not quantity

E.  a shift in demand is not possible