Your network includes 40 servers that run Windows Server 2008 R2. You plan to virtualize the servers by using Hyper-V in a failover cluster.  Your plan must allow for up to two offline host servers while still maintaining highly available virtual machines. You need to recommend the minimum number of Hyper-V host servers for the cluster.  How many servers should you recommend？（）

• A、three
• B、four
• C、five
• D、six