In English, if you want to indicate an exclusive alternativity (does that sound right?) or, you would say "either A or B". Therefore, to suggest non-exclusivity, you would say, "A or B": "They are looking for someone who knows Arabic or Chinese" (this does not mean they will turn down someone who knows both languages). Curiously, in some circumstances, "A and B" is what you need: "in his long and distinguished career he has been a writer, a film director, and a callboy" (this does not imply that he was all these things at the same time, but neither does it exclude the possibility). Here, to say, "or" would imply that he's been one of these three, but you don't know which or at least aren't telling. (In Slovene, btw, this sentence would probably be written with the conjunction "ali" – "or".) Sometimes "and" and "or" can mean (i.e. refer to) the same thing: "They are looking for people who know Arabic and Chinese" may mean essentially the same thing as "They are looking for people who know Arabic or Chinese" (i.e., they are looking for people who know Arabic and for people who know Chinese, and if you fall into either or both of these categories, they have a job for you), or it may not (if they do in fact require knowledge of both languages, but then they should say, "people who know both Arabic and Chinese"). If you want to underscore the possibility of the alternatives being non-exclusive, then you could say "A or B, or both".