单项选择题 You are creating a Windows Communication Foundation (WCF) service that uses claims-based authorization. The following code retrieves the correct claim set.var claims = ServiceSecurityContext.Current.AuthorizationContext.ClaimSets[0];You need to validate that the requesting client application has included a valid DNS value in the claim. Which code segment should you use to retrieve the claim for validation?（）

单项选择题 You create a Windows Communication Foundation (WCF) service. It is deployed on Microsoft Internet Information Services (IIS) with an application pool running as Network Service. You enable WMI tracing before launching the service. Your IT support staff adds WMI data collection through ASP.NET WMI tracing.You need to restrict the collection of WMI data to a privileged account. What should you do in WMI Control in the Computer Management console?（）

单项选择题 You are developing a Windows Communication Foundation (WCF) service that does not operate on a duplex channel.You find that operations do not start until all previous operations have finished. The service hosting code contains the following lines.var service = new WarehouseService(); var host = new ServiceHost(service);You need to ensure that new operations do not wait for previous operations to finish. Which attribute should you use to decorate the service?（）