If Firms in a Monopolistically Competitive Industry Are Operating with Positive

If firms in a monopolistically competitive industry are operating with positive economic profit, over time we would see

A) firms alter their advertising rates until they made at least normal profits.
B) some firms entering the industry, causing the market supply curve to shift to the right, lowering price.
C) some firms entering the industry, causing the demand curves of the existing firms to shift to the left.
D) some firms entering the industry, causing the demand curves of the existing firms to shift to the right.