Explanation:
There are two key features of Automatic Undo Management: Oracle manages all undo space automatically and undo tablespaces contain all undo information not stored in the SYSTEM rollback segment.
Incorrect Answers:
2: The SYSTEM rollback segment is created automatically during database creation and is managed automatically just as it was in previous versions.
4: AUM creates automatic undo segments itself based on gathered statistics about rollback requirements. Regular rollback segments are not gradually replaced with automatic undo segments, because these types of segments cannot coexist in one database instance.
5: The number of automatic undo segments available to an instance is not determined by the number of undo tablespaces defined in its initialization parameter file: AUM performs this task.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 160-164
Chapter 3: Manageability Enhancements
Oracle 9i New Features, Robert Freeman, p. 19-25
Chapter 1: Oracle9i Database Administration and Management Features

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