单项选择题

A.Stop the applications in all data volume groups and shut the system down during the outage period.
B.Stop the applications in datavg, unmount all datavg filesystems, varyoff datavg, and export datavg.
C.Stop the applications in datavg, unmount all datavg filesystems, and reduce datavg by the SAN disks.
D.Use the 'cpvg' command with the -z option to copy and compress datavg to different physical volumes.