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 day