Sentences that have never been introduced
I was just asked to transliterate: C'est à peu près le même pour nous.
Which I'd never heard before, not to mention the fact that its meaning is still, to me, pretty obscure. It remains very frustrating to get slammed errors like this. Keep it fair, introduce sentences in predictable ways. I still think Duolingo is better than not learning anything, but introducing random guessing like this makes this point hard to prove.