A Windows Communication Foundation (WCF) solution exposes the following contract over an HTTP connection.[ServiceContract]public interface IDataService{ [OperationContract] string GetData（　）;}Existing clients are making blocking calls to GetData. Calls to GetData take five seconds to complete.You need to allow new clients to issue non-blocking calls to get the data, without breaking any existing clients. What should you do?（）

• A、
• B、
• C、Generate a proxy class with asynchronous methods and use it for the new clients
• D、Add a new endpoint to the service that uses a full-duplex binding and use it for the new clients.