It is one of those "air quotes". Balaton is a lake, not a sea. So, you can think of it as
Lake "magyar tenger" Balaton.
Hopefully the exercise accepts it without the quotes, as well.
Here you go, you get one from me as well :) I feel with you because I just got this one marked as incorrect, too.
Oh, thank you~
I think we should dig a channel and connect the Balaton to the Mediterranean, so it becomes an actual part of a sea and we can throw out those silly quotation marks here. That sounds like a good idea.