You are creating a Window Commnunication Foundation (WCF) service application. The application needs to service many clients and requests simultaneously. The application also needs to ensure subsequent individual client requests provide a stateful conversation. You need to configure the service to support these requirements. Which attribute should you add to the class that is implementing the service?（）

• A、[ServiceBehavior(lnstanceContextMode = lnstanceContextMode.PerSession, ConcurrencyMode = ConcurrencyMode.Single)]
• B、[ServiceBehavior(lnstanceContextMode = lnstanceContextMode.PerCall, ConcurrencyMode = ConcurrencyMode.Reentrant)]
• C、[ServiceBehavior(InstanceContextMode = lnstanceContextMode.PerSession, ConcurrencyMode = ConcurrencyMode.Multiple)]
• D、[ServiceBehavior(lnstanceContextMode = lnstanceContextMode.PerCall, ConcurrencyMode = ConcurrencyMode.Multiple)]