Routers A and B are connected with a point-to-point OC-3 interface. Each router’s OC-3 interface is configured for both Level 1 and Level 2. The routers are configured in different areas.How many IS-IS adjacencies exist between the two routers？（）

A.Sending out a graceful restart PDU
B.Sending an LSP that contains no TLVs.
C.Sending out a restarts TLV with the RR bit set.
D.Reflooding its LSP with a maximum sequence number.

A.Router A must have a Level 2 adjacency with the Level 1/Level 2 router in area 49.0001.
B.The Level 1/Level 2 router in area 49.0001 sets the "attached" bit in the Level 2 LSP it floods into area 49.0001.
C.The Level 1/Level 2 router in area 49.0001 sets the "attached" bit in the Level 1 link-state PDU （LSP） it floods into area 49.0001.
D.The Level 1/Level 2 router in area 49.0001 advertises these prefixed into area 49.0001 using a Level 2 LSP it floods into the area.

A.broadcast hellos
B.Level 1 LAN hellos
C.Point-to-point hellos
D.Level 2 point-to-point hellos