[单项选择]Consider two markets; one has a Herfindahl-Hirschman Index (HHI) of 50, while the other has a four-firm concentration ratio equal to 2%. Which of the following statements most accurately describes these two markets() A. Both of these markets are monopolies. B. The market with the HHI equal to 50 is very competitive, while the other market has low competition. C. Both markets are highly competitive.