A system administrator has been asked to migrate the dev_vg volume group from server A to server B. The dev_vg volume group contains a single filesystem named "/development". To prepare for migration， which of the following is the correct sequence of commands for removing the volume group from server A？（）

• A、exportvg dev_vg； umount /development； varyoffvg dev_vg
• B、varyoffvg dev_vg； umount /development； exportvg dev_vg
• C、umount /development； exportvg dev_vg； varyoffvg dev_vg
• D、umount /development； varyoffvg dev_vg； exportvg dev_vg