Explanation:
Oracle uses special technique to perform full backups of data files: the server process reads the entire file and skips blocks that never been used. The FULL option of the BACKUP command in R MAN specifies a full backup, which is similar to an incremental level 0 backup, in which the full datafile will be copied to the backup set. The main difference is that a full backup will save every block in a datafile (except for datafile blocks that have never been used), while an incremental level 0 backup will skip empty blocks.
Incorrect Answers:
1: The server process reads and backs up the entire file except blocks that have never been used.
3: The server process will not skip blocks assigned its temporary segments.
4: The server process will not skip blocks that currently are not being used.
5: The server process will not skip blocks that are unchanged from the last backup.
Oracle 8, DBA Certification Exam Guide, Jason S. Couchman, p. 632-637
Chapter 13: Overview of Backup and Recovery

---