You are the Microsoft Lync administrator for a company that uses Lync Online.
The company has mandated that employees may use Lync Online to communicate with contacts from approved external domains.
You need to configure Lync Online to allow Lync federation with only three specific domains. You must achieve this goal by using the least amount of administrative
effort.
Which two actions should you perform? Each correct answer presents part of the solution.

A.
In the Lync admin center, set the External Access option to On except for blocked domains.

B.
In the Office 365 admin center, add the three domains to the domain list and set the domain intent for each domain to Lync Online.

C.
In the Lync admin center, set the External Access option to Off completely.

D.
In the Lync admin center, set the External Access option to On only for allowed domains.

E.
In the Lync admin center, configure the Presence Privacy Mode option to display presence information only to the users’ contacts.

F.
In the Lync admin center, add the three domains to the Blocked Or Allowed Domains list.

Explanation:
http://solveit.openjive.com/post/2014/01/27/Lync-Federation-with-Office-365Lync-Online
http://technet.microsoft.com/en-us/library/hh852512.aspx
http://technet.microsoft.com/en-us/library/jj205126.aspx