A recently installed package needs to be rolled back to a previous version. Which of the following commands will perform the task？（） 

A.Add root user to the /etc/hosts.equiv on serverb
B.Create $HOME/.rhosts file for the root user on serverb
C.Restart the rshd daemon with root enabled option on serverb
D.Add entry to allow root user from serverA to the /etc/hosts.allow on serverb

A.mksysb -r
B.savevg -r
C.restorevg -r
D.restorevgfiles

A.init 0
B.telinit m
C.shutdown -FM
D.sh /etc/rc.maint