Even in Spanish it is wrong, but who knows what Germans are like. In Spanish "Todas las personas estamos.............. It is the same idea. The verb refers to a group of people. I think maybe the original sentence on here was "Nobody is Perfect." which is correct English and than Duolingo changed it to this for some reason because the original commenter above us, up there, lol uses "Nobody is Perfect."
A) Natural Language Processing is one of the hardest problems in Computer Science today. Google Translate is far from perfect, and unless it statistically generated different correct translations each time you typed in the same sentence on the left hand side, it's only able to show you one correct answer, even though there could be dozens.
B) According to the following six links, "None of us are" is perfectly valid, and is often the only valid construction. The last link is a citation for the fifth and sixth links.
Also, "none of us is" and "none of us are" typed into Google with quotes both return about 25 million results (i.e. similar amounts).
Also, Ray Charles has a song titled "None Of Us Are Free" that was covered by both Lynyrd Skynyrd and Solomon Burke.
For our specific example, Oscar Wilde wrote a play in 1895 called "The Importance of Being Earnest" that has the exact words "None of us are perfect" in Act II.
Michael Huffington, a former congressman, is quoted as saying, "None of us are perfect, and we all make mistakes. But the American people are a very forgiving people."
I am believing that both are correct in this one example since None (which is really 'not one') can refer to "not a single person", or "not one or more people":
"None of us IS perfect." = "Not a single ONE (member) of us (our group) is perfect." (Singular subject = IS)
"None of us ARE perfect." = "Not ONE or even SEVERAL (members) of us (our group) are perfect." (Plural subject = ARE)
Maybe it's a stretch, but I'm thinking this is not just an exception to the rule. This is an example of NONE meaning "Not one or more" instead of just "Not (a single) one".
That's just my logic, anyway.
The correct way to say this in English is "None of us are perfect." Are is plural so it is referring to us. Are is referring to the entire phrase 'none of us". Prepositional phrase or something like that in English. None is singular by itself, but it is part of a prepositional phrase and the entire phrase "None of us" is plural so you would use "are" which is also plural.
The preposition "von" is always followed by a dative. That has nothing to do with being part of the subject or being located after "keiner". The dative is "uns".
But I think that was not the original question. The question was why is it "keiner".
"keiner" is the masculine nominative form. It is the subject of the sentence, so it needs to be nominative, and you usually use the masculine form if you don't know the gender of the persons or you have a mixed group. If you are talking about a group consisting solely of women you'd say "keine von uns".
"keine" is feminine for "not a" or "no" (when referring to quantity), "Keiner" means nobody (I'm not entirely sure though what the difference between "niemand" and "keiner" is, since they are both accepted in a sentence, even though I've heard that "keiner" is more common and I think that it can only be used in a sentence while "niemand" is more versatile but I may be wrong)
If you say "No one is perfect," it implies that not one person in the whole world is perfect. The sentence above is not referring to everyone in the world. It's talking about "not one of us" [being perfect]. Consider the difference between, "Not one of us is blue-eyed," compared to, "No one is blue-eyed."
Keiner (kein er) without a noun means "kein Mensch" (der Mensch) and is about the same as "niemand" (nobody). For example: Keiner ist perfekt. Otherwise "keiner" needs a "von" (with dative) or a genitive "der". For example: der Nachbar (the neighbour): keiner der Nachbarn or keiner von den Nachbarn; das Kind: kein(e)s der Kinder or kein(e)s von den Kindern; but a child would say: keiner von uns (Menschen); die Katze: keine der Katzen or keine von den Katzen. Keine is also the feminine form of kein.
Grammar Point none of When you use NONE OF with an uncountable noun, the verb is in the singular: None of the work was done. When you use NONE OF with a plural noun or pronoun, or a singular noun referring to a group of people or things, you can use either a singular or a plural verb. The singular form is used in a formal style in British English: None of the trains is/are going to London. None of her family has/have been to college
The phrase "Keiner von uns" implies "none of us." This not the same as "no one." None of us are grammar experts, but others (not among us) are experts. If you really mean to say that no one (or nobody) is perfect, then you would say "Niemand ist perfekt." No one knows what life in another universe is like.
I don't quite understand why so many comments are saying that the correct English is "None of us IS perfect". This sounds extremely awkward, and should be "none of us ARE perfect"
The German sentence is something I understand to mean something like "Nobody out of us is perfect", and in this scenario, "IS" is the correct conjugation because the focus of the sentence is on the singular word "nobody". in the example, the focus is on the plural word "us" and therefore the correct English is "none of us ARE perfect"