A prefix segment is a global segment, so a prefix SID is globally unique across the segment routing domain. An adjacency segment is a local segment, so the adjacency SID is locally unique for a particular router. https://www.cisco.com/c/en/us/td/docs/iosxr/ncs5500/segment-routing/61x/b-segment-routing-cg-ncs5500/b-segment-routing-cg-ncs5500_chapter_01.pdf

Selected Answer: D Option D is correct. An adjacency segment is identified by a label called an adjacency SID, which represents a specific adjacency, such as egress interface, to a neighboring router. The adjacency SID is distributed by IS-IS or OSPF. The adjacency segment steers traffic to a specific adjacency. About Segment Routing: An adjacency segment is a local segment, so the adjacency SID is locally unique relative to a specific router Read the "Segments" section: https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/segment-routing/configuration/guide/b-seg-routing-cg-asr9k/b-seg-routing-cg-asr9k_chapter_010.pdf