I think this should also accept the singular form with "kinek"
These are all accepted solutions:
Kinek van lova a városban?
Kiknek van lovuk a városban?
Kiknek van a városban lovuk?
Kinek van a városban lova?
Bad translation to Hungarian.
And I think the "kiknek van lovuk a városban" is also good translation
Correct translation is "Kiknek van lova a városban?" - the accepted translation is actually "Who in the ciry has horses?"
"Kiknek a városban van lovuk?"
is having "van" after "a városban" so bad, that it should not be accepted?