Your network contains two Exchange Server 2010 SP1 mailbox servers.

You create a database availability group (DAG).

You need to install all of the Failover Clustering components on the Mailbox servers.

What should you do?

A.
Add both servers to the DAG.

B.
Install the Application server role on both servers.

C.
Run Setup /roles:Mailbox /NewCMS on both servers.

D.
Run the Start-ClusterMailboxServer cmdlet on both servers.

Explanation:
Reference:

http://technet.microsoft.com/en-us/library/dd298065.aspx