"To whom does he reply?"
Translation:Σε ποιον απαντά;
"To who does he reply?" sounds incorrect to me.
I would say that the options are "To whom does he reply?" (most "correct" according to traditional grammar, sounds fairly formal to many present-day speakers), "Whom does he reply to?" (a bit less "correct" in the eyes of some, since the sentence ends in a preposition), and "Who does he reply to?" (even less "correct" in the eyes of some, since it uses "who" for the object of a preposition, but possibly the most widespread version).
The sort of people who care about the rule "don't end a sentence with a preposition" also tend to care about preserving the who/whom distinction -- the "to who" variant mixes conservative grammar with modern grammar and I'm not sure whether it's found in the wild.
It't not correctly accepted.