You have an Active Directory forest that contains three sites named Site1， Site2， and Site3. Each site contains two Exchange Server 2007 Client Access servers， two Mailbox servers， and two Hub Transport servers. All Exchange Server 2007 servers have Exchange Server 2007 Service Pack 1 （SP1） installed.You need to ensure that you can deploy Exchange Server 2010 servers in Site1.You must achieve this goal by using the minimum amount of administrative effort. What should you do？（）

• A、Upgrade all Client Access servers in the organization to Exchange Server 2007 Service Pack 2 （SP2）.
• B、Upgrade all Exchange Server 2007 servers in Site1 to Exchange Server 2007 Service Pack 2 （SP2）.
• C、Upgrade all Exchange Server 2007 servers in the organization to Exchange Server 2007 Service Pack 2 （SP2）.
• D、Upgrade all Exchange Server 2007 servers in Site1 and all Client Access servers in the organization to Exchange Server 2007 Service Pack 2 （SP2）.