You work as a Software Developer for ABC Inc.

You work as a Software Developer for ABC Inc. The company uses Visual Studio .NET 2008 as its application development platform. You create an ASP.NET Web application using .NET Framework 3.5. You create a Web form in the application that permits users to provide personal information. You add a DropDownList control to the Web form to retrieve the residential status of users. The default item that the DropDownList control displays is the "Select Country" option. You have to ensure that users select a country other than the default option. Which of the following validation controls should you use to accomplish this task?