Your network consists of a single Active Directory domain. All domain controllers run Windows Server 2008 R2. The network contains 100 servers and 5,000 client computers. The client computers run either Windows XP Service Pack 1 or Windows 7. You need to plan a VPN solution that meets the following requirements: èStores VPN passwords as encrypted text èSupports Suite B cryptographic algorithms èSupports automatic enrollment of certificates èSupports client computers that are configured as members of a workgroup What should you include in your plan?（）
- AUpgrade the client computers to Windows XP Service Pack 3. Implement a stand-alone certification authority （CA）. Implement an IPsec VPN that uses certificate-based authentication.
- BUpgrade the client computers to Windows XP Service Pack 3. Implement an enterprise certification authority （CA） that is based on Windows Server？2008 R2. Implement an IPsec VPN that uses Kerberos authentication.
- CUpgrade the client computers to Windows 7. Implement an enterprise certification authority （CA） that is based on Windows Server 2008 R2. Implement an IPsec VPN that uses pre-shared keys.
- DUpgrade the client computers to Windows 7. Implement an enterprise certification authority （CA） that is based on Windows Server 2008 R2. Implement an IPsec VPN that uses certificate-based authentication.