You work as a database administrator for Certkiller .com. You are using Recovery Manager （RMAN） to perform backups in your databases.  Which four backup operations can be performed using RMAN？（）

A.A backup of the target database when it is mounted

B.A backup of online redo log files when the database is open

C.A backup of only used data blocks in the file beingbeingbackup up

D.A backup of online， read/write data files when the database is open

E.A backup of only those data blocks that have changed since a previous backup

F.A backup of online， read/write data files when the database is in the NOMOUNT state.