You require the Oracle server to manage the undo segments and space among various active sessions automatically. You created an undo tablespace， UNDO_TBS1， in your database. Which two additional steps would you perform to achieve this？（）

• A、Set the UNDO_RETENTION parameter to 900 or more.
• B、Create an initial undo segment in the undo tablespace.
• C、Enable the retention guarantee for the undo tablespace.
• D、Set the UNDO_TABLESPACE parameter to UNDO_TBS1.
• E、Set the UNDO_MANAGEMENT initialization parameter to AUTO.