A Windows Communication Foundation (WCF) service that handles corporate accounting must be changed to comply with government
regulations of auditing and accountability. You need to configure the WCF service to execute under the Windows logged-on identity of the calling application.
What should you do?

A.
Within the service configuration, add a ServiceAuthorization behavior to the service,
and set ImpersonateCallerForAllOperations to true.

B.
Within the service configuration, add a ServiceAuthenticationManager behavior to the service,
and set ServiceAuthenticationManagerType to Impersonate.

C.
Within the service configuration, add a serviceSecurityAudit behavior to the service,
and set serviceAuthorizationAuditLevel to SuccessOrFailure.

D.
Within the service configuration, add a ServiceCredentials behavior to the service,
and set type to Impersonate.

Explanation:
// Code to create a ServiceHost not shown.
ServiceAuthorizationBehavior MyServiceAuthoriationBehavior = serviceHost.Description.Behaviors.Find<ServiceAuthorizationBehavior>();
MyServiceAuthoriationBehavior.ImpersonateCallerForAllOperations = true;

Delegation and Impersonation with WCF
(http://msdn.microsoft.com/en-us/library/ms730088%28v=VS.90%29.aspx)