Answer: Option (d) is correct.
Explanation:
Correct option: Only a perfectly competitive firm operates at its efficient scale.
In the perfectly competitive market and in the long run, the firms who are making losses will exit the market and those firms who are able produce at a point where price is equal to the average total cost will exist in the market.
However, monopolistic firms operates at a below efficient level of production and with an excess capacity.
Competitive firms are generally enjoys the productive efficiency in the long run because these firms have the capability to produce at a lower average total cost.
