Translation:Men are people.
Korean doesn't have words for A, the, etc. and instead has particles like 는/가, etc.
Though not necessarily correct 100% of the time, on duolingo it's widely accepted/pushed to have 는/은 translate to a more general audience (using 'a'), and 가/이 translate to a more specific item/group (using 'the').
But like I said, those 2 aren't always translatable like that, since context will change things in an actual conversation. But since duolingo doesn't provide context, it's generally pushed by duolingo to use the words A and The with their counterparts as what I said in the paragraph above.
But also, without context, using either 는/가 is fine if there's a choice for both with simpler sentences like this.
It got flagged as incorrect because you need the article "a" in English. As another user pointed out, "Man is person" is not correct in English. The translation should be "A man is a person." Your answer was pretty close; just don't forget that the article needs to be there in English in the same way it needs to be there in Korean :)
Hey!!! "Man is a person" should be right!! Isn't that too basic?? Isn't your system too standard??? Your coverage is not wide enough!! I know it's hard, but that's how it has to be. Isn't the translation in this app lacking?? Not all of us always use basic words. And we don't know if it's singular or plural. So, please correct this error so that we are more comfortable in learning. Thanks.
I'm not fluent in Korean, but yes, it's "ibnida". Anything ending in -ㅂ니다 is the formal version of the verb "to be," so 사라밉니다 should mean "is a person/are people." Anything ending with -ㅂ니다 uses ㅂ, which is romanized as "b," making it "ibnida," but it's pronounced as "imnida" (I think the pronounciation is different because of the ㅂ coming after and "i" sound and before and "n" sound). So it's pronounced as 임니다, but it's spelled as 입니다.