Under the model of monopolistic competition, a$($an$)\_\_\_\_\_\_\_\_$ in the number of firms in the industry will cause $\_\_\_\_\_\_\_\_$ to $\_\_\_\_\_\_\_\_.$

A$)$ increase; average price; decrease

B$)$ increase; average price; increase

C$)$ increase; average cost; decrease D$)$ decrease; markup; decrease

E$)$ increase; marginal cost; decrease