A. A backup set that is missing one or more backup set pieces
B. A backup that has exceeded the retention criteria and is no longer needed
C. A backup set that does not include archived redo logs
D. A backup set that can not be recovered due to corruption
E. A backup set superceded by a datafile copy

A. Recover database datafiles from physical disk backup sets.
B. Recover required incremental backups from physical disk backup sets.
C. Recover required archived redo logs from physical disk backup sets.
D. Apply incremental backups to recover the database. 
E. Apply archived redo logs to recover the database.