You use Microsoft .NET Framework 4 to

You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application.  You write the following code fragment. You need to implement the MyProject.AverageConverter class.  What should you do?（）

• A Implement the IValueConverter interface.
• B Implement the IMultiValueConverter interface.
• C Inherit from the TypeConverter class.
• D Apply the TypeConverterAttribute attribute.