The correct answer is option C) the four largest firms account for 52% of total industry sales. A four-firm concentration ratio is a measure of the total percentage of an industry's sales that are generated by the four largest firms in that industry. It indicates the concentration of market power in the hands of the four largest firms. In this case, the four-firm concentration ratio for industry X is 52. This means that the four largest firms in the industry account for 52% of total industry sales. Based on this ratio, we can conclude that the industry is oligopolistic in nature because it is dominated by a few large firms that hold a significant market share. Thus, the correct answer is option C) the four largest firms account for 52% of total industry sales.