You executed the following command in Recovery Manager （RMAN）： RMAN> RESTORE CONTROLFILE; Which operation must you perform before this command is executed？（）
A. back up the control file to trace
B. bring database to the MOUNT state
C. open a connection to the RMAN recovery catalog， which contains the RMAN metadata for the target database
D. set the database ID （DBID）， but only if the DB_NAME parameter associated with the target database is unique in the recovery catalog
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