Why would you execute the report obsolete command？（）  

• A、 To list all backups that were no longer available for restore operations
• B、 To list all backups that had aged beyond the RMAN retention criteria
• C、 To list all backup set pieces listed in control-file or recovery-catalog metadata that are not on the backup media
• D、 To list all datafiles that are no longer part of the database and thus do not need to be backed up
• E、 To list all archived redo logs that are no longer needed for any database recovery