"Which cats are they?"
Translation:Welke katten zijn het?
In English, "it" plural is "they". In Dutch, "it" plural is "it". I figured that all or most animals, including humans, reproduce sexually, and have male and female, the pronouns "hij" and "zij" would be appropriate for them. If the answer we are given here is correct, it would seem that "hij" and "zij" are reserved for humans. If so, I would consider the usage misguided, but if that is how the word is used, it is what it is, and we can either go along or try to change it.