Your production database is running in archivelog mode and you are using recovery manager （RMAN） with recovery catalog to perform the database backup at regular intervals. When you attempt to restart the database instance after a regular maintenance task on Sunday， the database fails to open displaying the message that the data file belonging to the users tablespace are corrupted.  
The steps to recover the damaged data files are follows：  
1. Mount the database 
2. Open the database 
3. Recover the data file 
4. Restore the data file 
5. Make the data file offline 
6. Make the data file online  
Which option identifies the correct sequence that you must use to recover the data files？（）