It would be nice if this sentence even made sense.
There are many interpretations of this sentence possible, and therefore many different ways to translate this, many of those ways are probably not included in the model answers.
I heard we can also use "Qual a resposta...?" (without "é") Any thoughts?
Yes, Qual é can be shortened in informal speech to just Qual
I've been seeing Qual used as "which" and O que used as "what", why does that differ here?