Answer:
d. 1.0.
Step-by-step explanation:
Four-firm concentration ratio is the ratio of the sales of the four largest firms in the industry relative to total industry sales. In industry B total sales is of $10 million and the top four combined have total sales of $10 million
Therefore, the four firm concentration ratio = $10 million/ $10 million = 1
Therefore correct answer is option B i.e. 1.0