B: The auto-failover groups feature allows you to manage the replication and failover of some or all databases on a logical server to another region.
C: The auto-failover group must be configured on the primary server and will connect it to the secondary server in a different Azure region.

Incorrect:
Not A: Geo-replication failovers require client applications to change their connection strings.
Reference:
https://docs.microsoft.com/en-us/azure/azure-sql/database/auto-failover-group- overview?tabs=azure-powershell#best-practices-for-sql-database
https://docs.microsoft.com/en-us/azure/azure-sql/database/failover-group-add-single-database- tutorial?tabs=azure-portal