"Are they writing a book?"
Translation:Schreiben sie ein Buch?
The noun "Buch" is neuter (das Buch), so it takes the neuter accusative "ein" instead of the masculine "einen". Hope that helps!
You don't need to use "are" in this case is German, so the structure is wrong because it's a question so the verb goes first.
Why don't we need 'are' in this case? I've seen other sentences say 'Are you__?'
Thanks for you response but because you need to use 'Sind' doesn't necessarily mean it's wrong and 'Sind' is a verb.
So, I wrongly wrote: "Schreiben ein Buch sie?"
Duolingo corrected me with this: You used the wrong word. "Schreiben sie 1 Buch?"
(That is a cut and paste...so, yes, the number 1 is being suggested for ein, I guess. I don't think Duo got the answer any more correct then I did this 1 time.)