Yeah, I'm not surprised. I thought of that when giving the answer, and I just "knew" that it would want the masculine plural. Duo doesn't seem to get all the right versions from the start; it seems to require a fair amount of correction to get all possible versions. The 'safest' way to get the answer 'right' by Duo is to give the most common version (most of the time; and sometimes it just has some weird answer it really is insisting on...)
I don't see the problem with 'Vous etes surs' meaning you are sure, it cannot be a question because there is no question mark and this phrase could easily be part of a larger utterance. For example 'OK, so you are sure, Amy is sure and Tom is sure. We are just waiting on Beth's decision'. RKSMT don't get so defensive it doesn't seem like anyone is attacking you through these comment, they are simply trying to explain when this phrase might realistically be used. You asked the question and they tried to answer.
Yes, "Vous êtes sûrs" can be "You are safe." As an adjective, it can mean sure, confident, reliable, trustworthy. http://www.larousse.com/en/dictionaries/french-english/s%C3%BBr/74718
I always use the singular informal rather than the singular formal.
My guess is that Duo wants to make sure you don't avoid remembering the difference by just using singular formal ie: vous êtes for both singular and plural.
It seems to me that if you use vous êtes then you have to use sûrs because it has to be consistent throughout the phrase.
It's a safe bet, when using French, to apply the masculine form unless feminine is indicated by the context.
For me the exercise was Select the missig word and the beginning of the sentence was "Vous êtes ....." with the following choises: "sûrs", "sûr" and "sûre". The only accepted answer is "sûrs". Why? We have no context to tell us whether it is formal singular or simply plural. Then why is not both "sûr" and "sûrs" acceptable? And in what situations would "sûre" be correct?
"You all", or "you-all", or "y'all" differs substantially from "you" (pl) in that it is a very distinct regionalism.
I know Southerners are always trying to convince everybody else that we should all use "you-all" because it is convenient to make a distinction between "you" (sing) and "you"(pl), but the fact is nobody does use it except some people in the southern US.
There are quite a number of people doing this DL course whose are not fluent in English (and I remain deeply impressed that anyone would attempt such a thing). I really think it does them a great disservice to suggest that "you all" is exactly equivalent to "you" (pl). because if they actually believed it and tried to use "you all" in conversation, I'm afraid the result would be outright hilarity, which would be rather embarrassing for them.
Merriam-Webster has "you-all": <http://www.merriam-webster.com/dictionary/you-all>
I recognize that the words "you all" can occur in an ordinary English sentence, with the specific meaning, "all of you", similar to your example. "You all need to go...." It would be used when the speaker wanted to emphasize the inclusive nature of "all", i.e., each and every one of you, without exception.
This still does not in any way make the term equivalent to the simple plural "you". For one obvious reason, it could not apply in the case of only two people, when it would have to be "you both".
In the original query that all of this has descended from, the questioner wanted to know why "you all" was not accepted as a translation of "vous". And the answer remains, that "you all" is only regarded as an expression of the 2nd person plural in certain regions of the English-speaking world.
To me that's not an obvious reason, simply because the count would need to be three or more. "You(pl)" can be conveyed with greater clarity by the use of "all" or a numeric count, etc. Therefore I refuse to be held hostage to saying only "you". Thankfully the English language is extremely rich and flexible.
@chris_naim - I have no idea what "tout le monde o chacun" could mean. It doesn't look like French to me.
You say that one cannot say "Tous vous, etc.", but you can say "vous tous", ex: Merci à vous tous = thanks to you all
Note that the "you all" is a perfectly fine translation, since the "tous" is in the French sentence. It is no longer a variant form of plural "you", but another way of saying "all of you".
There are a couple of other ways to ask, as well: You can just say, "Vous êtes sûrs?" with a rising inflection, just as you might do in English, i.e., "You are sure?"
Another very common way of constructing a question is to put "Est-ce que" on the front, so: "Est-ce que vous êtes sûrs?" (literally, "Is it that you are sure?")
I once joined an online French-learning discussion group, and one of the other parties expressed enormous skepticism that "anyone would actually use all those words to ask a simple question". In fact, she was pretty sure somebody was pulling her leg - us, or perhaps the French in general. Ha - so I must assure you that this format is extremely common and heard every day.
Just as an general enquiry, many years ago I was taught to go with the 'Est-ce que' construction just about every time. We did just a little inversion but I cannot recall any simply "Est-ce" being used. Is this likely to be a change in teaching/my memory, or does it reflect a particular mode of use or more relaxed style. Hope you do not mind the question.
Why does everyone think that "Sûr" should be correct? It does not matter if you are talking to only one person or more people, when you use vous, then shouldn't the verbs and adjectives be used accordingly? To elaborate, in my native language we have the exact same thing, ti (which is tu) and vi (which is vous). Vi ste sigurni (You are sure) it does not matter if you are talking to one person respectively or to more people, you will pretty much always say it that way.