A. When multiple hard disks fail, the level of the RAID group is downgraded from RAID5 to RAID0, the system can still write data to the hard disk and the previous data will not be lost

B. When multiple hard drives fail, the RAID group level is downgraded from RAID5 to RAID0, and the system can still write data to the hard drives, but the previous data will be lost

C. When multiple hard disks fail, the level of the RAID group is downgraded from RAID5 to RAID0. If the hard disk fails again, the data cannot be recovered

D. When multiple hard disks fail, after the RAID group level is downgraded from RAID5 to RAID0, if the hard disk fails again, the data will continue to be restored