does Polițistul specifically mean police officer? What then do you call a policeman? Is this again the American usage, or is it an attempt to be non-sexist?
"Policeman" and "police officer" are nearly interchangeable, except in cases where you want to avoid the suffix "-man". But, in Romanian, all nouns have a gender anyway, so, usually, the male form of it is used and there aren't any genderless alternatives.
Also, AFAIK, duolingo uses American English exclusively...