A wrong use of the pronoun "nich"--it should be "ich". A mistake easy to make, usage of both pronouns is similar. We would say: "Nie znasz ich" (You don't know them), but "Nie wiesz niczego o nich" (You don't know anything about them). "Nich" would be used after a preposition--in the first sentence it is not there, in the second it is the preposition "o" (about).
It's a month down the line and the sentence is still "Nie znasz nich.". Did you report it at the time? Or did you decide in the end it was valid?
Mistakes need to be reported, otherwise how will the DuoLingo team know.
Other native polish speakers! What do you think, is this sentence wrong?
Dzięnki bardzo mihxal!
Will the next person who reads this please report this polish sentence as wrong please? (Go back to the question and press the button underneath to the left of "Discussion")
"Nie znasz nich" should be "Nie znasz ich"
(I would report it but I'm out of this section now and don't know exactly how to quickly link back to the actual exercise.)