The root (/) file system is mirrored with a primary and secondary submirror. What is the last step that must be performed on a SPARC-based system so that the system boots automatically from the secondary submirror when a primary submirror fails?

A.
use the setenv command to set the auto-boot? variable to false

B.
use the nvalias command to redefine the device alias disk so that it references the primary submirror

C.
use the nvalias command to define a backup_root device alias, which references the secondary submirror

D.
use the setenv command to redefine the boot-device variable so that it references both the
primary and secondary submirrors