Correct Answer:
Explanation/Reference:
Note:
* A database availability group (DAG) is a set of up to 16 Microsoft Exchange Server 2013 Mailbox servers that provide automatic database-level recovery from a database, server, or network failure. When a Mailbox server is added to a DAG, it works with the other servers in the DAG to provide automatic, database-level recovery from database, server, and network failures.
* You can specify a name for the DAG and the witness server that you want to use, and leave the Witness directory field empty. In this scenario, the task will create the default witness directory on the specified witness server.
* If the witness server you specify isn’t an Exchange 2013 or Exchange 2010 server, you must add the Exchange Trusted Subsystem universal security group to the local Administrators group on the witness server. These security permissions are necessary to ensure that Exchange can create a directory and share on the witness server as needed.
Reference:
http://technet.microsoft.com/en-us/library/dd351172(v=exchg.150).aspx