Your network contains a single Active Directory domain. All domain controllers run Windows Server 2008 R2. There are 1，000 client computers that run Windows 7 and that are connected to managedswitches. You need to recommend a strategy for network access that meets the following requirements： èUsers are unable to bypass network access restrictions. èOnly client computers that have up-to-date service packs installed can access the network. èOnly client computers that have up-to-date anti-malware software installed can access the network. What should you recommend？（）

A. Implement Network Access Protection （NAP） that uses DHCP enforcement.
B. Implement Network Access Protection （NAP） that uses 802.1x enforcement.
C. Implement a Network Policy Server （NPS）， and enable IPsec on the domain controllers.
D. Implement a Network Policy Server （NPS）， and enable Remote Authentication Dial-In User Service （RADIUS） authentication on the managed switches.