Was that wrong? I thought it could be that because I answered another one earlier with "The boy questions the girl" and it was using the same verb as used here and it was right... For this one it seemed more natural to me to try "The boy asks and the girl answers" which was correct, so I'm not sure if using "questions" was wrong :/
See Lundgren8 above – förhör and ifrågasätter are better translations of the verb 'questions'. It is possible that this translation is currently accepted somewhere, but it still isn't a good one.
"explain" is förklara. I mean, the girl could be answering a question without explaining something. :)
We accept "The boy asks and the girl answers" and "The boy is asking and the girl is answering", but I don't think it makes a lot of sense to mix them up.
It may not be colloquial or literary usage but it is definitely not grammatically incorrect. As to adding it or not, it is totally up to you. :)
Remembering my childhood though I'd sooner say "Pojken frågar inte men flickan svarar".