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