Explanation:
If the backup or copy is no longer available, then RMAN marks it as EXPIRED. If it was marked EXPIRED and is now available, then RMAN marks it AVAILABLE. Incorrect Answer:
1: Backup sets, backup pieces, and copies can have the status AVAILABLE, EXPIRED, or UNAVAILABLE. You can view the status information in the output of the LIST command and the recovery catalog views.
2: It does not mark it as OBSOLETE.
4: It does not mark it as UNKNOWN.
Reference:
OCP Oracle 9i Database: Fundamentals II Exam Guide, Rama Velpuri, p. 269-270
Chapter 11: RMAN Backups

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