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 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.
C. 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.
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， Router A will  maintain the role of master virtual router.

A. R1
B. R2
C. The AVG
D. The AVF
E. None of the other alternatives apply