I thought it would be кто знает ответ на этом вопросе, because на would require the prepositional case here, but I was wrong
I thought the same, but can anyone clarify why the prepositional case was not used here?
Prepositional case is only used with на when talking about where something is located. When talking about movement TO a place, or knowing the answer TO a question, accusative is used.
And this makes sense considering that этот is accusative, masculine, similar as well. Right?
кто знает ответ этого вопроса - not possible to say?
No, your variant would sound really weird.
Why not "Кто знает ответА на этот вопрос"? I thought that abstract nouns can take the genitive ending instead of the normal accusative when they are direct object.
Only if it's a negative sentence, as far as I know
Would it sound okay to say "кто знает ответ для этого вопроса?"
Why isn't ответ in accusative?
It is. Accusative has the same form as nominative for masculine inanimate nouns.
It accepted "эту вопросу" but I guess it shouldn't have.