You administer an Access Control Service namespace named contosoACS that is used by a web
application. ContosoACS currently utilizes Microsoft and Yahoo accounts. Several users in your
organization have Google accounts and would like to access the web application through
ContosoACS. You need to allow users to access the application by using their Google accounts.
What should you do?

A.
Register the application directly with Google.

B.
Edit the existing Microsoft Account identity provider and update the realm to include Google.

C.
Add a new Google identity provider.

D.
Add a new WS-Federation identity provider and configure the WS-Federation metadata to point to the Google
sign-in URL.

Explanation:
Configuring Google as an identity provider eliminates the need to create and manage
authentication and identity management mechanism. It helps the end user experience if there are
familiar authentication procedures.
http://msdn.microsoft.com/en-us/library/azure/gg185976.aspx