Correct me if I'm wrong, but this sentence means "which are your shoes", right? So the answer "which is your footwear" is not a right solution since it is not plural, and shoes are not the same as footwear. Or if we accept approximate solutions like that, we could also accept answers like "which are the boots". But it is not an accident that we have dozens of different words for things we put on our feet, so why mix up these?
Cuales = which ones
Cual = which one
Cual es... = which one is...
Cuales son... = which ones are...
If they are in an interrogative sentence, remember to add accent "á": Cuál, cuáles
'Cual' is singular, 'cuales' is plural, as in 'the shoeS'. Not just 1 of the pair.
How am I suppose to differentiate between "¿Cualés son tu zapatos?" and "¿Cualés son tus zapatos?" in hearing (as in opposition to the same words in writing)?
I think because "¿Cualés son tu zapatos?" would be wrong, so you can presume you wouldn't be tested with a gramatically incorrect sentence.