You work as a database administrator for Supportcenter.cn. You want to create your database with the automatic undo management feature enable.Which two tasks must you perform to achieve this？（）

A. Set the UNDO_RETENTION parameter to AUT
B. Create an initial undo segment in undotablespace.
C. Set the UNDO_RETENTION parameter to 900 or more
D. Set the initialization parameter UNDO_MANAGEMENT to AUTO
E. Set the UNDO_MANAGEMENT parameter to the name of an undotablespace