"We walked through the dense forest."
Translation:Ni promenis tra la densa arbaro.
Doesn't "tra" take the accusative when one completely crosses through something? Am I just too optimistic?
Tra already means to cross something completely. The n-ending means the the motion continues outside. But this can also be the meaning of the form without n. The n-form is used only if it really matters that the motion continues.
So, then, this sentence should make sense with the accusative. I was actually thinking, honestly, of soldiers having to cross a dense forest (I was putting together an ancient history course at the time). I would have suggested that it should have been accepted, but I just was not sure.
I thought 'arbaro densa' would be ok too since the order is not prescribed. But duolingo marks it wrong. Is 'densa arbaro' the only right option?
Of course, to report it (now that you've read this thread), you'd have to put that same answer in again - but knowing that densa arbaro is the better answer, why would you?