Examine the CREATE DISKGROUP command used to create a disk group：   SQL> CREATE DISKGROUP misc EXTERNAL REDUNDANCY  DISK ’ORCL： FRA3’ NAME misc1， ’ORCL： FRA4’ NAME misc2；   In which situation would you use this method of disk group creation？（）

• A、 When two-way disk mirroring is required for the allocation units
• B、 When three-way disk mirroring is required for the allocation units
• C、 When using hardware mirroring or RAID
• D、 When disk mirroring is required for the Automatic Storage Management （ASM） disks