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