655.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
正确答案是A