Which element of Azure SQL Database supports adaptive query processing?

Automatic Index Tuning is the correct answer because it directly relates to adaptive query processing in Azure SQL Database. This feature automatically identifies and applies the best indexing solutions for improving query performance based on the workload patterns. It adapts to changes in workload, ensuring that the indexing strategy evolves as the database usage changes over time. This dynamic approach to managing indexes helps optimize query execution, making it a key component of adaptive query processing.

On the other hand, elements like Query Store track query performance metrics and help troubleshoot and optimize queries but do not actively adjust or tune processing. Elastic Pools are aimed at optimizing resource usage across multiple databases but are not specifically focused on adaptive query processing. Dynamic Data Masking primarily serves to protect sensitive data and does not contribute to query performance adjustments.