单项选择题 You executed the following query：  SELECT operation， undo_sql， table_name  FROM flashback_transaction_query  Which statement is correct regarding the query output？（）

单项选择题 By mistake， you ran the batch job （for updating the BILL_DETAILS table） twice. You are not sure which rows in the BILL_DETAILS table were affected. You need to identify：  a） a list of changes made along with the transaction identifier of each change  b） the necessary SQL statements to undo the erroneous changes  Which option would you choose？（）

单项选择题 You are working in an online transaction processing （OLTP） environment. You realize that the salary for an employee， John， has been accidentally modified in the EMPLOYEES table. Two days ago， the data was in the correct state. Flashback logs generated during last two days are available in the flash recovery area.  Which option would you choose to bring the data to the correct state while ensuring that no other data in the same table is affected？（）