"Bread is food."
I wrote "빵이 음식입니다" and it was marked as wrong. But shouldn't it be equally as correct as "빵은 음식입니다"? Because when you write 빵은, you are saying "independent of other things, bread is food". But when you write 빵이, you are saying that, specifically, bread is food.
So they can both be correct in answer to different questions. And since we aren't given the preceding question, both should be accepted.
은(after consonant) 는(after vowel) are topic markers/particles. That indicate that the conversation is currently talking about bread. So all follow up statements would be about bread
I think it's the other way around. But I got marked incorrectly for using the subject marker anyway, so I am also confused. :P