Answer :
It's not A because "its'" means that there's more than one cat that hurts its leg. The correct answer would be B, because the word "its" means that it belongs to someone or something. And the cats leg belongs to it, so it's B. Here is an example: The dodo bird is known for its inability to fly. In this case the dodo birds inability to fly is what belongs to it.
The correct answer is B. because there are no error and its does not need any apostrophes.
