The key characteristics of a monopolistically competitive industry are: [a] a large number of firms that sell differentiated products that are close substitutes. [b] firms can easily enter or exit a monopolistically competitive industry. [c] because monopolistically competitive firms can increase their profits if they can successfully distinguish their products from those of their rivals, they have an incentive to engage in sales promotions and advertising. for each of the examples below, indicate which of the above characteristics (a, b or

c. is being illustrated. there are a number of fast-food restaurants in town, and they compete fiercely. some restaurants cook their hamburgers over open flames. others fry their hamburgers. in addition, some serve broiled fish sandwiches, while others serve fried fish sandwiches. a few serve ice cream cones for dessert, while others offer frozen ice cream pies