You are maintaining your OLTP database in Oracle10g. You are performing the Flashback Transaction Query to find the undo SQL statements that can be used to undo the changes made to the database in the specific time period. Which pseudocolumn will you use to perform the Flashback Transaction Query？（）

You are performing flashback of the ORDERS table in the Scott’s schema because some important data is deleted in the table by mistake. The SCN number was 771513 at the time of deletion. You issued the following statement to perform Flashback Table： 
SQL> FLASHBACK TABLE ORDERS TO SCN 771513；  
What is the prerequisite to perform Flashback Table？（）

You are working as a DBA at NetFx Corporation. A user， Scott， is maintaining the records of all the employees in the EMPLOYEEtable. Initially， the salary of the employee， ’E0025’， was $1800. On 1 May 2004， the salary of the employee， ’E0025’， was increased by $200.  
The user， Scott， issued the following statement to modify the record of the employee， ’E0025’：  
SQL>UPDATE EMPLOYEE  SET SALARY = 2000  
WHERE EMPNO = ’E0025’；  
SQL>COMMIT；  
On December 1， 2004， the salary of the employee， ’E0025’， was increased by $400. The user， Scott， issued the following statement to modify the record of the employee， ’E0025’：  
SQL>UPDATE EMPLOYEE  SET SALARY = 2400  
WHERE EMPNO = ’E0025’； 
 SQL>COMMIT；  
On July 1， 2005， the salary of the employee， ’E0025’， was increased by $500. The user， Scott， issued the following statement to modify the record of the employee， ’E0025’  
SQL>UPDATE EMPLOYEE  SET SALARY = 2900  
WHERE EMPNO = ’E0025’；  
SQL>COMMIT；  
On July 5， 2005， the HR manager asked you to generate the increment report of the employee， ’E0025’， for the period between 1 May 2004 and 1 July 2005. Which flashback feature will you use to generate the increment report？（）