An RMAN backup job&ens

An RMAN backup job fails， displaying the following error message：  ORA­19809： limit exceeded for recovery files  Your analysis shows that the Flash Recovery area is full. What would you do to resolve the error？（）

• Aincrease the value of UNDO_RETENTION
• Bchange the value of WORKAREA_SIZE_POLICY to AUTO
• Cincrease the value of DB_RECOVERY_FILE_DEST_SIZE
• Dincrease the value of CONTROL_FILE_RECORD_KEEP_TIME