You have an Exchange organization.All servers in the organization have Exchange Server 2010 Service Pack 1 （SP1） installed. The organization contains a database availability group （DAG） named DAG1.DAG1 contains three Mailbox servers including a server named Server1. Server1 fails.You restore Server1.You need to ensure that Server1 can replicate mailbox databases from DAG1. What should you do first？（）

• A、Remove the default mailbox database from Server1.
• B、Modify the GUID for Server1.
• C、Remove the object for Server1 from DAG1.
• D、Disable log truncation for the mailbox databases in DAG1.