Which two are prerequisites for performing a flashback …

Which two are prerequisites for performing a flashback transaction?

A.
Flashback Database must be enabled.

B.
Undo retention guarantee for the database must be configured.

C.
EXECUTE privilege on the DBMS_FLASHBACK package must be granted to the user flashing back
transaction.

D.
Supplemental logging must be enabled.

E.
Recycle bin must be enabled for the database.

F.
Block change tracking must be enabled tor the database.

Explanation:
http://docs.oracle.com/cd/E11882_01/appdev.112/e41502/adfns_flashback.htm#ADFNS611 To configure your
database for the Flashback Transaction feature, you or your database administrator must:
With the database mounted but not open, enable ARCHIVELOG:
ALTER DATABASE ARCHIVELOG;Open at least one archive log:
ALTER SYSTEM ARCHIVE LOG CURRENT;
If not done, enable minimal and primary key supplemental logging:
ALTER DATABASE ADD SUPPLEMENTAL LOG DATA;
ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (PRIMARY KEY) COLUMNS;
If you want to track foreign key dependencies, enable foreign key supplemental logging:
ALTER DATABASE ADD SUPPLEMENTAL LOG DATA (FOREIGN KEY) COLUMNS;
Oracle Database Advanced Application Developer’s Guide 11g, Using Oracle Flashback Technology