A cluster running 19c Grid Infrastructure supports both Oracle 11g to 19c RAC databases using ASM.
The COMPATIBLE.ASM, COMPATIBLE.RDBMS, and COMPATIBLE.ADVM parameters are currently set to 11.2 for all diskgroups.
You must support these capabilities in all diskgroups:
1. ACFS Replication
2. ACFS Encryption
To what minimum values must the compatible attributes be set?
To support ACFS Replication, all compatibility attributes must be set to at least 12.1. The COMPATIBLE.ADVM must specifically be 12.1 for ACFS Encryption. However, to continue supporting Oracle 11g databases, we cannot set COMPATIBLE.ASM or COMPATIBLE.RDBMS higher than 11.2. Therefore, setting COMPATIBLE.ASM to 11.2, COMPATIBLE.RDBMS to 12.1, and COMPATIBLE.ADVM to 12.1 is the safest configuration that ensures the needed features while maintaining compatibility with 11g.
B - wrong - it will not allow the database 11.2 to run on the diskgroup with 12.1 compatible.rdbms.