What are three main phases of an attack？（）

A.SCREEN options are deployed at the ingress and egress sides of a packet flow.
B.Although SCREEN options are very useful， their use can result in more session creation.
C.SCREEN options offer protection against various attacks at the ingress zone of a packet flow.
D.SCREEN options examine traffic prior to policy processing， thereby resulting in fewer resouces used formalicious packet processing.

A.RADIUS
B.TACACS+
C.LDAP
D.IIS

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 is unreachable， authentication is not performed.
D.If the local password database is not configured in the authentication order， and the configured authentication server rejects the authentication request， authentication is not performed