You are the messaging engineer for your company. The company has a main office and four branch offices. You are currently running Exchange Server 2007. Each office contains two clustered Mailbox servers, one Hub Transport server and one Client Access server. You need to recommend a solution for e-mail delivery redundancy on your network in case a Hub Transport server fails. Which solution should you recommend?

A.
In each office, install the Client Access server role on a new server.

B.
In each office, install the Hub Transport server role on a new server.

C.
Run the Setup.exe /roles:HT command on each active clustered Mailbox server.

D.
Run the Setup.exe /roles:HT command on each passive clustered Mailbox server.