You have enabled backup optimization in RMAN. You issue the following RMAN command to configure a redundancy-based retention policy：   CONFIGURE RETENTION POLICY TO REDUNDANCY 3；   Which statement is true？（）  

• A、 The command fails because you cannot configure a redundancy-based retention policy when backup  optimization is enabled
• B、 Backup optimization is performed， but RMAN considers the redundancy-based retention policy when it determines which datafiles should be backed up
• C、 Backup optimization is permanently disabled
• D、 Backup optimization is temporarily disabled because a redundancy-based retention policy is specified