D Question 17 4 pts Which of the following statements is true of oligopoly models? O If oligopoly firms compete with each other without colluding, they always end up with zero economic profit. Once formed, colle sive agreements are generally easy to hold together. O In oligopolies, less product differentiation generally results in greater economic profits. O Some oligopoly models show how firms can compete with each other without collusion and still maintain positive economic profit in the long run. 4 pts