A company named Fabrikam, Inc. is deploying an Office 365 tenant. You install Active Directory Federation Services (AD FS) on a server that runs Windows Server
2012.
The company’s environment is described in the following table:

You must obtain a certificate from a certification authority and install it on the federation servers.
You need to specify the subject name for the certificate.
Which name should you specify?

A.
fs.fabrikam.com

B.
serverl.fabrikam.com

C.
fabrikam.com

D.
server2.fabrikam.com

Explanation:
http://blogs.technet.com/b/askds/archive/2012/01/05/understanding-the-ad-fs-2-0-proxy.aspx