You create a Windows Workflow Foundation application by using Microsoft .NET Framework 3.5. You plan to add a workflow to implement an order processing logic. When the host initiates the order processing logic, it raises an event named StartProcessing. You need to configure the local communication interface to enable the workflow to handle the event. Which code segment should you use?

A.
public interface IContract{ event EventHandler<ExternalDataEventArgs> StartProcessing;}

B.
public class Contract : ExternalDataExchangeService{ event EventHandler<ExternalDataEventArgs> StartProcessing;}

C.
[ExternalDataExchange]public interface IContract{ event EventHandler<EventArgs> StartProcessing;}

D.
[ExternalDataExchange]public interface IContract{ event EventHandler<ExternalDataEventArgs> StartProcessing;}