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.
Or "We've had a similar experience." or "We are in a similar situation" ... . As kimojima says, don't expect word-for-word translations.
New lessons occasionally throw up new idioms. I'm also generally a bit taken aback at first, but usually, the new phrase has been repeated several times by the time the lesson is over and it is thereby added to my precarious new acquisitions.