A.The backup performed on Sundays contains all the blocks that have ever been used in the database.
B.The backup performed on Sundays contains all the blocks that have changed since the last level 1backup. 
C.The backup performed on each working day contains all the blocks that have changed since the lastlevel 0 backup.
D.The backup performed on Monday contains all the blocks that have changed since the level 0 backup，and every other working day contains all the blocks that have changed since the level 1 backup.

A.You can perform consistent backups only.
B.You can perform a complete database backup without shutting down the database instance.
C.You can back up data files only when all data files have the same SCN recorded in the control file.
D.You can back up only those data files whose headers are frozen by using ALTER TABLESPACE BEGINBACKUP or ALTER DATABASE BEGIN BACKUP commands.