正解:B
Cisco TrustSec uses tags to represent logical group privilege. This tag, called a Security Group Tag (SGT), is used in access policies. The SGT is understood and is used to enforce traffic by Cisco switches, routers and firewalls . Cisco TrustSec is defined in three phases: classification, propagation and enforcement.
When users and devices connect to a network, the network assigns a specific security group.
This process is called classification. Classification can be based on the results of the authentication or by associating the SGT with an IP, VLAN, or port-profile (-> Answer A and answer C are not correct as they say "assigned ... on a switch" only. Answer D is not correct either as it says "assigned to each router").