单项选择题

A. Implement a RADIUS request attribute policy to assist with realm selection and create different role-mapping rules for the user in each realm.
B. Implement a directory/attribute server on the realm and set up this server to determine by group membership the proper role to which a user should be mapped.
C. Reorder the role-mapping rules to allow for the more open role to be mapped first and then enable the "stop processing rules when this rule matches" function on this role.
D. Implement a Host Checker policy on the realm that determines the geographic location of the device and restricts the user based on the results of the policy.