Oh dear! My correct translation of "Is this a licence" was marked incorrect in favour of "Is this a license". In English as opposed to American English the noun form of licence is licence. If it is written "license" it is the verb form which might work in America but not in other English speaking nations. I can see an argument for accepting both but not for disallowing a perfectly correct answer.
8 April 2019 - DUO after 5 odd years, this error has still not been corrected, despite so many English people pointing out the mistake. Whether it is a patent or a driving permit, as a noun the word should be written with a "c" i.e "licence". Confirming that in English it is only written with an "s" i.e. "license" if it is a verb. Reported. Duo please review. Thank you.
Subtle difference in the meanings of those two sentences in English, the way I see it. "Is this a licence?" is asking if this single piece of paper in front of me is indeed a licence, (or is it something entirely different, like a concert ticket). "Is this ONE a licence" suggests that of a number of pieces of paper, you are indicating one piece, and asking if that piece is the one that is the licence. And yes, I am aware that I am spelling licenCe with a C. The noun form of that word can (should!) be spelled that way, it is only the verb form that uses an S.