Assume that in a monopolistically competitive industry, firms are earning economic profit. This situation will:

attract other firms to enter the industry, causing the existing firms' profits to shrink.

Explanation:

Monopolistic competition can be defined as an imperfect competition where many producers or organizations sell differentiated products that are not perfect substitutes. Examples of firms or organizations engaging in a monopolistic competition are restaurants, shoes, clothing lines etc.

Generally, a monopolistic competitive market is characterized by the presence of large numbers of firm (producers) and a very low entry barrier.

Hence, in a monopolistic competition, firms have a degree of control over price, make independent decisions and can freely enter or exit the market in the long-run. Therefore, these firms combine elements of both monopoly and competition.

When a monopolistically competitive firm is in long-run equilibrium marginal revenue is equal to marginal cost (MR = MC) . This ultimately implies that in the long-run, firms engaging in monopolistic competitive market are often going to manufacture the quantity of goods where the marginal cost (MC) curve intersect with the marginal revenue (MR). Also, the price set would be greater than the minimum average total cost (ATC).

Hence, assuming that in a monopolistically competitive industry, firms are earning economic profit. This situation will attract other firms to enter the industry, causing the existing firms' profits to shrink.

going on the gulag might you to find a better answer for that problem

answer; tech (a) is correct;