[单选]

You are creating an application that consumes a Windows Communication Foundation (WCF) service. The service implements the IService contract. The client application contains the CallbackHandler class, which implements IServiceCallback.You need to ensure that a client proxy is created that can communicate with the service over a duplex channel.
Which code segment should you use?（）

下列各项投资对象中，其流动性较弱，一般要保持到到期日的证券是（）。 国库券。 短期融资券。 可转让存单。 银行承兑汇票。 原型法是一种基于（）的系统开发方法。 接受式开发策略。 直线式开发策略。 迭代式开发策略。 实验式开发策略。 Your network contains a client computer named Computer1 that runs Windows 7. Computer1 is configured to use DirectAccess. You need to identify the URL of the network location server that Computer1 is configured to use. What should you do？（） From a command prompt, run ipconfig.exe /displaydns.。 From a command prompt, run netsh.exe namespace show policy.。 From Control Panel, run the network adapter troubleshooter.。 From the Network Connection Status window, view the Network Connection Details.。 明式家具的设计特色：一是注重结构美，二是注重材质美，三是注重（），四是注重装饰美。 造型美。 色彩美。 形式美。 简洁美。 重章复沓

You are creating an application that consumes a Windows Communication Foundation (WCF) service. The service implements the IService contract. The client application contains the CallbackHandler class, which implements IServiceCallback.You need to ensure that a client proxy is created that can communicate with the service over a duplex channel.
Which code segment should you use?（）