Just correcting what I said:

a) Archivelogs and online redologs after backup available; database in ARCHIVELOG => Restore control files and datafiles and then recover (answer #3)

That's wrong. If all files were restored, control file would be in sync with datafiles (no recovery needed).

The correct would be:
a) Archivelogs and online redologs after backup available; database in ARCHIVELOG => Restore only the missing datafile and then recover (no answer).

That's a Sybex question. Maybe it would be better to give up understanding what they meant :P