"What are you worrying about?"
Translation:Czym się martwisz?
'o czym się martwisz' was rejected. Is this so different to 'o co się martwisz'? If so a hint to why, please.
In Polish it should be accusative (o kogo? o co?) or locative (czym?). „o czym” is wrong.
ahh so am I right in saying that because czym is the locative version of co and anything following "o" is locative, we can assume here that czym = "o co"?
Not everything following "o" is Locative. It's Locative when "o" = "about" = "on what topic" - so actually not here. Those remaining cases that don't take Locative take Accusative.
So "O co się martwisz?" is the literal translation, while "Czym się martwisz?" (which basically means the same) is more like "What worries you?", although grammatically the subject is different ('By what are you worrying?', something like that).