You are upgrading the database servers that are used by all of the companys applications. As the first step in the upgrade, you upgrade the development database servers. You need to verify that the upgrade of the database servers did not introduce any errors into the databases. What should you do?（）

A. Execute unit test scripts for each stored procedure in each database.
B. Execute the stored procedures in the SQL Server Management Studio debugger, and verify the results.
C. Set the database compatibility level on the database servers to 80.
D. Execute the application user interface test scripts to verify proper operation.