4. Competitive firms differ from monopolies in which of the following ways? (i) Monopolies are price makers while competitive firms are price takers (ii) Marginal revenue for a competitive firm equals the price, while marginal revenue for a monopoly is less than the price (iii) Monopolies must lower their price ingrderto sell more of their product, while competitive firms do not a. (i) and (ii) b. (ii) and (iii) c. (U and (iii) d. (i), (ii), and (iii)