A. Router A is the master virtual router, and Router B is the backup virtual router. When Router A fails, Router B will become the master virtual router. When Router A recovers, Router B will maintain the role of master virtual router.
B. Router A is the master virtual router, and Router B is the backup virtual router. When Router A fails, Router B will become the master virtual router. When Router A recovers, it will regain the master virtual router role.
C. Router B is the master virtual router, and Router A is the backup virtual router. When Router B fails, Router A will become the master virtual router. When Router B recovers, Router A will maintain the role of master virtual router.
D. Router B is the master virtual router, and Router A is the backup virtual router. When Router B fails, Router A will become the master virtual router. When Router B recovers, it will regain the master virtual router role.