Your database instance is configured with automatic undo management and the UNDO_RETENTIONparameter is set to 900 seconds. You executed the following command to enable retention guarantee: SQL> ALTER TABLESPACE undotbs1 RETENTION GUARANTEE; What effect would this command have onthe database（）

A. The extents in the undo tablespace retain data until the next full database backup.
B. The extents containing committed undo in the undo tablespace are not overwritten for at least 15 minutes.
C. The extents containing committed data in the undo tablespace are not overwritten until the instance is shutdown.
D. The extents containing committed undo in the undo tablespace are transferred to Flash Recovery Areabefore being overwritte