Which two actions should you perform?

Your company plans to migrate from On-Premises Exchange to Exchange Online in Office
365.
You plan to integrate your existing Active Directory Domain Services (AD DS) infrastructure
with Azure AD.
You need to ensure that users can log in by using their existing AD DS accounts and
passwords. You need to achieve this goal by using minimal additional systems.
Which two actions should you perform? Each answer presents part of the solution.

A.
Configure Password Sync.

B.
Set up a DirSync Server.

C.
Set up an Active Directory Federation Services Server.

D.
Set up an Active Directory Federation Services Proxy Server.

Explanation:
Ref: http://technet.microsoft.com/en-us/library/dn441214.aspx