For an Azure App Service using a user-assigned managed identity to connect to Azure SQL Database with Microsoft Entra authentication, the required database-side step is to create a database user from the external provider, then grant the needed database roles. Microsoft's Azure SQL documentation for managed identities states that to let a managed identity access the target database, you create a SQL user for that identity by using:

CREATE USER [<identity-name>] FROM EXTERNAL PROVIDER;

and then assign the appropriate roles.

That makes db_datareader and db_datawriter the right role grants here, because the requirement says the identity must have read and write permissions to SalesDB.

The other options are incorrect:

A uses CREATE LOGIN ... FROM EXTERNAL PROVIDER, which is not the right choice for this Azure SQL Database scenario; the documented pattern is to create a database user from the external provider.

B and D create SQL-authentication principals with passwords, which does not meet the Microsoft Entra managed-identity requirement.

D also grants sysadmin, which is a server-level overgrant and not appropriate for the stated read/write requirement.