Explanation:
The database chooses a System Commit Number within a five minutes of the time specified.
Incorrect Answers:
1: It chooses a SCN within a five, not one minute, of the time specified.
2: The database does not choose a System Commit Number within an one second of the time specified.
4: The database chooses a System Commit Number within a five minutes of the time specified, not 5 seconds.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 45-47
Chapter 2: Availability Enhancements
Oracle 9i New Features, Robert Freeman, p. 63-68
Chapter 3: New Oracle9i Availability and Recoverability Features

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