"Maria is a foreigner."
It is not necessary, just more polite to add さん, or くん, or any of the other name suffixes there are. This sentence is the rude and very informal way of saying it.
But マリアさんは外国人です should be accepted. I typed it and it was not accepted, with only the さん missing in the "correct" translation
I did this as well, and was disappointed to find that I got it wrong. Duolingo has taken care to almost always promote the formal/polite way of saying everything (teaching the extremely formal ではありません vs the extremely common じゃない). Seems odd they'd miss this here.
If they're going to be rude about it, why not go a step further and use 外人 instead of 外国人？
That's a fair call, but including or not including さん is considerably more complicated than "being/not being rude".
Contrary to what @StevenPaul5 said, マリアは外国人です is not informal, and not necessarily rude. Formality and politeness are not always one and the same in Japanese.
Here, です is used, so the speaker is being "formal" (basic civilized society level formal; there are other higher levels of formality in Japanese) towards the listener. But by choosing not to use さん with Maria, the speaker indicates that they are either close friends with her or they have been explicitly told by Maria that she doesn't need to be addressed with さん and are respecting Maria's foreign-ness.
Further to this, the most likely explanation (setting aside any foreign complications) is the 内・外 うち・そと concept, which is central to Japanese society and essential to understanding social nuances.
To elaborate a little more, of the face of it, we should assume that Maria is part of the speaker's in-group (内), and that the listener is not.
Wow thank you for this nuanced response . I never would have thought of it this way. Crazy how nuance works in Japanese, it fascinates me!
You should definitely flag that. Unless you clicked さい (which appeared in ny word bank) thinking it was さん f(^_^;
I understand that -さん Is not necessary, but it marked it wrong, when it should also be perfectly acceptable.
So gaijin is rude because it eliminates the kanji for "country"? So instead of saying "person from a foreign country" you would be just saying "foreigner," which is less respectful.
I believe that you could translate it as "outsider" (外: "outside", 人: "person"), giving a connotation of "being outside of Japanese society".
No, 人 (じん) still means "person" here, as it did in アメリカ人. 外国 is literally made up of the kanji for "outside" and "country", which put together mean "foreign country".
It's just like how you have the word amerika for america and amerikajin for american
That's correct, you should flag it for the course developers (who don't necessarily read these comments) to fix.
if you omit the honorific suffix, but still use the です form, does it have a connotation of dehumanizing somebody?
No, not at all. The lack of honorific suggests that you and Maria are close friends or family. The use of です suggests that you aren't too familiar with the person you are speaking to, or that you are being polite/respectful to them.
Just to see if I've understood things right, would マリアが外国人です。 be more akin to "Maria is THE foreigner"? Or can が not be used at all in that sentence?
が can be used in this sentence, but it's not very common/natural in most situations I can think of. The difference between は and が is very difficult to explain, mostly because it comes down to the interplay between context and intention so it's hard to make consistent rules for. (Note, this is only for when you have to choose between the two, not when both are present in the sentence which is tricky too because which noun you assign to which particle depends on intended emphasis as well.)
The only scenario I could come up with where が would sound natural in is if you asked someone "you know that foreigner?" and they said "oh, you mean Ken?" to which you replied "no, Ken is short for Kentarou who is Japanese. Maria is the foreigner. (マリアが外国人です)"
So I would say マリア
は外国人です is more like "Maria is a foreigner", whereas マリア
が外国人です would be "Maria is a foreigner".