You are creating a workflow host application by using Microsoft .NET Framework 3.5. You use Windows Workflow Foundation to create the application. You need to ensure that the host application can receive method calls from the workflow instances. Which code segment should you use?

A.
WorkflowLoaderService loaderService = new
DefaultWorkflowLoaderService();workflowRuntime.AddService(loaderService);

B.
ExternalDataExchangeService dataService = new
ExternalDataExchangeService();workflowRuntime.AddService(dataService);

C.
ManualWorkflowSchedulerService scheduler = new
ManualWorkflowSchedulerService();workflowRuntime.AddService(scheduler);

D.
SqlWorkflowPersistenceService sqlService = new SqlWorkflowPersistenceService("<conn str>");workflowRuntime.AddService(sqlService);