Which two statements regarding external authentication servers for firewall user authentication are true?（） (Choose two.)

• A、Up to three external authentication server types can be used simultaneously.
• B、Only one external authentication server type can be used simultaneously.
• C、If the local password database is not configured in the authentication order, and the configured authentication server  bypassed.
• D、If the local password database is not configured in the authentication order, and the configured authentication server authentication is rejected.