Your network contains two Active Directory sites. The sites connect to each other by using a WAN link.  You plan to deploy two Exchange Server 2010 Mailbox servers and two Client Access servers in eachsite.  Each site will contain a Client Access array.  You need to recommend a solution to deploy Hub Transport servers. The solution must meet the following requirements： .Continue to deliver e-mail messages to users in other sites if a single Hub Transport server fails .Support the planned Client Access array deployment.Minimize the number of Exchange servers What are two possible ways to achieve this goal？（）

• A、Add the Hub Transport server role to each Mailbox server.
• B、Add the Hub Transport server role to each Client Access server.
• C、Deploy two Hub Transport servers on two new servers in each site.
• D、Deploy one Hub Transport server on a new server， and then install the SMTP service on each     ClientAccess server.