If there are many firms participating in a market, the market is either a. an oligopoly or monopolistically competitive. b. perfectly competitive or monopolistically competitive. c. an oligopoly or perfectly competitive. d. an oligopoly or a cartel.

In this case,the answer would be option b. or perfectly competitive or monopolistically competitive.

Explanation:

A perfect competitive market structure is commonly characterized by the presence of many firms or producers and buyers or consumers.The products or services sold in the perfectly competitive market are homogeneous or similar in nature,feature or characteristic.A monopolistic competition is identified as a particular type of market structure in which there are many firms or companies selling differentiated or heterogeneous products or services.Hence,monopolistic competition also consists of many or numerous firms or companies but unlike perfect competition,the products or services in monopolistic competition are differentiated or heterogeneous in nature,feature of characteristic.

A, a would be the answer.