Which binding element should you use?

You are using Windows Communication Foundation (WCF) to create a service.
You need to implement a custom message-level security binding element. Which binding element should you use?

A.
TransportSecurityBindingElement

B.
HttpsTransportBindingElement

C.
SslStreamSecuntyBindingElement

D.
WindowsStreamSecurityBindingElement

Explanation:
Three binding elements relate to message level security, all of which derive from the SecurityBindingElement class.
The three are TransportSecurityBindingElement, SymmetricSecurityBindingElement, and AsymmetricSecurityBindingElement.
The TransportSecurityBindingElement is used to provide Mixed mode security. The other two elements are used when the message layer provides security.

Additional classes are used when transport level security is provided:
* HttpsTransportBindingElement
* SslStreamSecurityBindingElement
* WindowsStreamSecurityBindingElement

How to: Create a Custom Binding Using the SecurityBindingElement
(http://msdn.microsoft.com/en-us/library/ms730305.aspx)