Examine the following ALTER command: SQL> ALTER DISKGROUP dgroup1 UNDROP DISKS; What is the purpose of the command?（）

• A、It cancels all pending disk drops within the disk group.
• B、It restores disks that are being dropped as the result of a DROP DISKGROUP operation
• C、It mounts disks in the disk group for which the drop-disk operation has already been co pleted
• D、It restores all the dropped disks in the disk group for which the drop-disk operation has already been completed
• E、It adds previously dropped disks back into the disk group