Near complete compatibility with on premises SQL Server is the correct option.

Azure SQL Database Managed Instance provides near native compatibility with the SQL Server engine so you can migrate existing on premises SQL Server instances with minimal application changes. The managed instance supports many instance scoped features such as SQL Server Agent, cross database queries, native backup and restore patterns, and other capabilities that make lift and shift migrations much easier compared with a single database deployment.

Cloud Spanner is incorrect because it is a Google Cloud product and not a benefit of an Azure service. Cloud Spanner is a different vendor offering that focuses on global scale and horizontal relational scaling.

Support for NoSQL APIs is incorrect because Managed Instance targets SQL Server relational workloads and does not provide NoSQL APIs. Azure offers NoSQL capabilities through services such as Cosmos DB which are designed for document and key value patterns.

Lower operational cost is incorrect because cost depends on sizing and features and is not the principal distinction between managed instance and a single database. Managed Instance reduces administrative effort and improves compatibility but it is chosen primarily for feature parity and easier migrations rather than guaranteed lower price.

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