You work in a company which is named Wiikigo Corp. The company uses SQL Server 2008. You are the administrator of the company database. Now you are in charge of a SQL Server 2008 instance. On two cluster-ready nodes, you intend to perform an installation of a SQL Server 2008 mission-critical cluster. Constant availability is needed by the mission-critical cluster. You have to configure the SQL Server cluster to failover and reduce the service disruption to the least. Which failover option should you use?（）  

• A、You should allow failback only during non-business hours 
• B、You should immediately allow failback
• C、You should prevent automatic failback 
• D、You should allow failback only during business hours