Following a successful migration，it is highly recommended that concurrent Volume Groups be Converted to enhanced concurrent capable Volume Groups.  In order to follow this recommendation，what step must be completed first？（）  

• A、 The Volume Groups must be changed with chvg -E vgname.
• B、 The Volume Groups must be a member of a resource group and must be varied on al nodes of       the cluster.
• C、 The Volume Groups must be a member of a resource group and must be varied off all nodes      of the cluster.
• D、 The Volume Grups cannot be changed to enhanced concurrent capable because they must be      recreated with mkvg -C vgname.