You are developing a WCF service. A new service instance must be created for each client session. You need
to choose an instancing mode. Which instance mode should you use?

A.
PerCall

B.
Single

C.
Multiple

D.
PerSession

E.
PerRequest

Explanation:
WCF Instancing Modes (http://msdn.microsoft.com/en-us/library/ms731193.aspx)