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 View the Exhibits. You performed operations on the DEPT4 table as shown in the Exhibit. When you perform the FlashbackVersions Query， you find that the first two updates are not listed. What could be the reason？（）