In BGP, community attributes help control the advertisement scope of BGP routes. Here’s what each option means:

No_Export: This well-known community attribute prevents BGP routes from being advertised to external BGP (EBGP) peers. Routes with this attribute can still be advertised to internal BGP (IBGP) peers within the same AS. This ensures that the route remains within the originating AS.

No_Advertise: This attribute means that the route should not be advertised to any BGP peer, whether internal or external.

Internet: Indicates that the route can be advertised to all BGP peers, both internal and external, with no restrictions.

No_Export_Subconfed: Similar to No_Export, but it also restricts advertisement to peers within a BGP confederation. It ' s more specific and not generally used just to keep routes inside one AS.

Therefore, the correct answer is B. No_Export, as it is the attribute that ensures BGP routes remain within the AS by not being sent to EBGP peers.