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.

（）是最基本的系统软件，是计算机系统本身能有效工作的必备软件。