The system was running a normal workload during the last 24 hours. You need to ensure that with the same workload you should be able to flashback tables by three hours. What would you do to find the system recommendations for the undo retention period and the undo tablespace size?（）

• A、set DB_FLASHBACK_RETENTION_TARGET=10800  
• B、create a new scheduler window for the time period of 24 hours and use the optimizer statistics 
• C、modify the Automatic Workload Repository (AWR) snapshot time interval to three hours and use ADDMfindings 
• D、specify New Undo Retention as three hours and Analysis Time period as Last One Day in the Undo Advisor page and use its recommendations