You are creating an application using Visual Studio 2010. The application consumes a Windows Communication Foundation (WCF) service.You are adding a service reference to the WCF service. You need to ensure that the generated proxy does not block the calling thread when executing a service method. What should you do when adding the service reference? （）

• A、Set the Collection type to ObservableCollection.
• B、Select the Reuse types in all referenced assemblies option.
• C、Select the Generate asynchronous operations option.
• D、Select the Always generate message contracts option.