Thanks :D I only suggested it because the use of "WHAT" and " FOR" can also be interpreted as why in colloquial speech, similar to "dla-czego".
For example: Q - Can i use your toilet? A - What are you asking for? You know where it is.
Thanks for that, BW, B91
Why is prosic biernik/accusative? I would have thought anything using the preposition 'o' would trigger locative.
"o" triggers Locative when it means "about" - so most often. But there are some cases when it means something different and takes Accusative. This is one of them.
"O czym Śpiewacie" is a prior exercise... seems odd that prosić does not require locative here. Is this just an exception without explanation?
Well, "o" generally takes Locative when it means "about", and even then it's actually only when "about" means "on the topic of" (so not "to worry about sb", for example).
So if it's not Locative, then it's Accusative.