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 hour