Your database is running under automatic undo management and the UNDO_RETENTION parameter is set to 900 sec. You executed the following command to enable retention guarantee： SQL> ALTER TABLESPACE undotbs1 RETENTION GUARANTEE; What effect would this statement have on the database？（）
A、The extents in undo tablespace retain data until the next full database backup.
B、The extents containing committed data in the undo tablespace are never overwritten.
C、The extents which no longer contain uncommitted data in the undo tablespace are not overwritten for at least15 minutes.
D、The extents containing committed data in the undo tablespace are not overwritten until the instance is shut down.
