You executed the following command in Recovery Manager （RMAN）： RMAN> RESTORE CONTROLFILE； Which operation must you perform before this command is executed？（）
- Aback up the control file to trace
- Bbring database to the MOUNT state
- Copen a connection to the RMAN recovery catalog， which contains the RMAN metadata for the target database
- Dset the database ID （DBID）， but only if the DB_NAME parameter associated with the target database is unique in the recovery catalog