You create a stateless, thread-safe service by using Microsoft .NET Framework 3.5.
You use the Windows Communication Foundation model to create the service.
Load testing reveals that the service does not scale above 1,000 concurrent users.
You discover that each call to the service instantiates a new service instance.
You also discover that these service instances are expensive to create.
You need to ensure that 5,000 concurrent users can access the service.
Which code segment should you use?

A.
[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall,
ConcurrencyMode=ConcurrencyMode.Reentrant)]

B.
[ServiceBehavior(InstanceContextMode=InstanceContextMode.Single,
ConcurrencyMode=ConcurrencyMode.Multiple)]

C.
[ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall,
ConcurrencyMode=ConcurrencyMode.Multiple)]

D.
[ServiceBehavior(InstanceContextMode=InstanceContextMode.Single,
ConcurrencyMode=ConcurrencyMode.Reentrant)]