An administrator is moving a volume group from one server to another. The disks will be physically moved between the two systems. Which two operations are required on the volume group prior to the physical disk switch?（）

• A、'varyoffvg' and 'exportvg'
• B、'varyofflv' and 'importvg'
• C、'varyofflv' and 'migratepv'
• D、'varyoffvg' and 'migratevg'