You create a Windows Communication Foundation service by using Microsoft .NET Framework 3.5.
You need to ensure that the following requirements are met:
Each client has its own session.
The client application makes method calls by using the same connection to the same service instance.
Which code segment should you use?

A.
[ServiceContract(SessionMode=SessionMode.Required)]
[ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]

B.
[ServiceContract(SessionMode=SessionMode.Required)]
[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerSession)]

C.
[ServiceContract(SessionMode=SessionMode.Allowed)]
[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall)]

D.
[ServiceContract(SessionMode=SessionMode.Allowed)]
[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerSession)]