"It has two kittens."
Translation:Sillä on kaksi pentua.
The original sentence is the Finnish one, not the English one. If they chose a sentence with "pentu", why not? It's a valid sentence in Finnish. Of course, it's ambiguous, as it can be puppies, kittens, cubs, and whatnot. I just hope they accept all these answers in English.
I think it sound silly anyhow. Nobody says 'sillä on kaksi kissanpentua' if we are talking about the mother cat. 'Sillä on kaksi pentua.' would be correct. A person might have two kittens as a pet and in informal speech one can say 'sillä on kaksi kissanpentua' meaning the human who has them as pets.