Explanation:
For correct closing of the database you can use SHUTDOWN NORMAL, SHUTDOWN IMMEDIATE, SHUTDOWN TRANSACTIONAL commands.
Incorrect Answers:
1: After this command you will need to perform instance recovery before, so this type of shut down the database is not good for a closed database backup.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 586-587
Chapter 12: Overview of Backup and Recovery

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