[单项选择] You are developing a Windows Communication Foundation (WCF) service that must be discoverable.You need to ensure that the ServiceHost instance supports multiple discovery versions. What should you do?（）
A. - Specify a unique DiscoveryVersion parameter for each endpoint constructor. - Use the same value for the Address property of each endpoint.
B. - Use the endpoint constructor without the DiscoveryVersion parameter. - Use a unique value for the Address property of each endpoint.
C. - Specify a unique DiscoveryVersion parameter for each endpoint constructor. - Use a unique value for the Address property of each endpoint.
D. - Use the endpoint constructor without the DiscoveryVersion parameter. - Use the same value for the Address property of each endpoint.

[单项选择] You are developing a Windows Communication Foundation (WCF) service.One of the service operations contains the following code.private static int counter = 0;[OperationContract]public void IncrementCount（　）{ counter++;}You need to set a service behavior that prevents two or more threads from incrementing the counter variable at the same time. Which code segment should you use to set the service behavior?（）
A. [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Single)]
B. [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession, ConcurrencyMode = ConcurrencyMode.Single)]
C. [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)]
D. [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall, ConcurrencyMode = ConcurrencyMode.Reentrant)]