What does "totally reduced" mean? My textbook mentions that:


  Iron is unable to be totally reduced... the most common non-zero oxidation states of iron is (o for oxidation, r for reduction) are: +2r, +3, +4o, +5o, +6o.


I thought it maybe meant going to $\ce{Fe^4+}$ (as the most reduced I commonly see is $\ce{Fe^3+}$), but then upon googling there is also $\ce{Fe^5+}$ ions, so how far does it have to go until it is totally reduced (if this is even what it meant by totally reduced)? Edit: Sorry, got reduction and oxidation mixed up (thanks for pointing this out DVSA). However, my question still stands, though replacing the above with more to e.g.  $\ce{Fe^4-}$ than  $\ce{Fe^3-}$  . 

The question, for context, is below (I have already typed up what I think are the relevant parts above). FYI the answer is D, but I want to know what B means.
Reduction means that electrons are added, you are talking about oxidation. I haven't heared the term "fully reduced" in this context before, but I guess it means a full shell. In case of iron this would mean a oxidation state of -10, while as far as I know the highest we can get is -4.

And don't confuse oxidation states with charge of ions.

Well, now that I see the actual question I think there's nothing to really understand here. Just a wrong, made up answer.