[单选题]The system was running a normal workload during th

Aset DB_FLASHBACK_RETENTION_TARGET=10800  

Bcreate a new scheduler window for the time period of 24 hours and use the optimizer statistics 

Cmodify the Automatic Workload Repository (AWR) snapshot time interval to three hours and use ADDMfindings 

Dspecify New Undo Retention as three hours and Analysis Time period as Last One Day in the Undo Advisor page and use its recommendations