If they wanted 'sit down' why not say in Hungarian leül? In English it really isn't needed anyway so should be correct as 'sitting on the furniture.'
That doesn't answer my question about why they didn't include the down pre-verb le- if in English they wanted to say sit down instead of just sit...
A problem here is that "sitting on the furniture" doesn't capture the movement (from standing to sitting) that the Hungarian sentence conveys with the -ra suffix.
"furniture" in English is a mass noun and uncountable.
It seems that in Hungarian, bútor is a count noun, equivalent to what would be "one piece of furniture" in English, and in the plural equivalent to (individual) "pieces of furniture" or, more generally (collective) "furniture".
two "corrects" solutions are given: 1. who is sitting down onto the furniture, and 2. who sits on the furniture. I see a problem in both cases. 1. le, is missing in the hungarian sentence. 2. "ra" is not the right suffix (maybe "butorokon"?), as I understand "ra" indicates a motion.
Sit down. Is ülj le in hungaryan. "Who sits down onto the furniture?" is ki ül le a butorokra? It is correct in hungaryan.