For the p5 590 and p5 595 servers, the HMC must be directly attached. Why is the use of a private service network between HMC and the p5 590 required?（）

A. The Bulk Power Controllers are dependent upon the HMC to provide them with DHCP addresses.
B. A firewall is required to isolate the private network from any of the open networks to which the HMC is attached.
C. Network communications can be implemented through an open network. No private network is required but it is recommended.
D. All p5 590 and 595 servers are shipped with one service processor card. A private network is required to manage DHCP addresses.