To enable faster incremental backups, you enabled block change tracking for the database.Which two statements are true about the block change tracking file?（）

• A、Multiple change tracking files can be created for a database.
• B、The change tracking file must be created after the first level 0 backup.
• C、RMAN does not support backup and recovery of the change tracking file.
• D、The database clears the change tracking file and starts tracking changes again, after whole database restore and recovery operations.