Refer to the Accompanying Graph

Refer to the accompanying graph. If all firms in a monopolistically competitive industry have demand and cost curves like those shown, we would expect that, in the long run,

A) all firms will leave the industry.
B) a certain percentage of existing firms will exit the industry.
C) firms in the industry earn negative economic profits.
D) new firms will enter the industry.
E) enough new firms will enter the industry that it will become perfectly competitive.