You work as the enterprise exchange administrator at TestKing.com. TestKing.com makes use of Microsoft Exchange Server messaging solution. The TestKing.com network is configured to run Exchange2010. The servers at TestKing.com are configured as follows：You are planning to make use of a distribution groups in the TestKing.com domain.  However，you have to propose the changes that you want to make to back you plan of action.（）

• A、The best proposal is to use TESTKING-EX14 as an expansion server which will hosts the distribution groups.
• B、The best proposal is to change the distribution groups with dynamic distribution groups.
• C、The best proposal is to upgrade TESTKING-EX13 to Exchange Server 2010.
• D、The test proposal is to make use of a Widnows Server 2008 R2 global catalog Servers.