Your company has several branch offices. Your network consists of a single Active Directory domain.   Each branch office contains domain controllers and member servers. The domain controllers run  Windows Server 2003 SP2. The member servers run Windows Server 2008 R2.  Physical security of the servers at the branch offices is a concern.   You plan to implement Windows BitLocker Drive Encryption （BitLocker） on the member servers.  You need to ensure that you can access the BitLocker volume if the BitLocker keys are corruptedon the member servers. The recovery information must be stored in a central location. What should you do？（）

• A、Upgrade all domain controllers to Windows Server 2008 R2.Use Group Policy to configure Public Key  policies.
• B、Upgrade all domain controllers to Windows Server 2008 R2. Use Group Policy to enable Trusted platform Module（TPM） backups to Active Directory.
• C、Upgrade the domain controller that has the schema master role to Windows Server 2008 R2. Use group Policy to enable a Data Recovery Agent （DRA）.
• D、Upgrade the domain controller that has the primary domain controller （PDC） emulator role to windows Server 2008 R2. Use Group Policy to enable a Data Recovery Agent （DRA）.