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 completed
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 grou