Identify two types of solutions in which you would need to use Active Data Guard...

a solution that provides zero-data-loss protection at any distance without impacting database performance

a solution for disaster protection and database rolling upgrades for a mission-critical OLTP database, where you also want to extract data from a data guard primary database for ETL update o' an enterprise data warehouse

a solution requiring minimal planned downtime and risk, using standby first patching, database rolling upgrades, and select platform migrations

a solution that helps with integrated automatic database and client failover between source and target, where you also need to establish advanced replication (such as multi master and bidirectional replication and data transformations)