You executed the following command in Recovery Manager （RMAN） against your Oracle 10g database：  RMAN> REPORT NEED BACKUP days 3;  What would be the output of this command？（） 

• A、a list of files that require a backup within three days
• B、a list of files that have not been backed up for three days
• C、a list of files that RMAN recommends be backed up only once in every three days， based on low volatility
• D、a list of files for which a backup has already been performed and may need a backup after three days