After you unregister a database from a recovery catalog, what happens to the backup metadata in the recovery catalog?

Answer: B

Explanation: The backup metadata is always maintained in the control file for a number of days specified by the initialization parameter CONTROL_FILE_RECORD_KEEP_TIME. A is incorrect because the control file always maintains the backup metadata and no migration is required. C is incorrect because all metadata for a database is removed from the recovery catalog when it is unregistered. D is incorrect because a database's metadata is removed immediately from the recovery catalog when it is unregistered.