Respuesta :
In the first sentence, the horse is referred to as it, so you should just continue using that pronoun. So the correct answer is The horse lost its rider, but it finished the race anyway.
The sentence in which the underlined pronoun is used correctly is the following one: The horse lost its rider, but it finished the race anyway.
The fact is that we should use the pronoun "it" when talking about animals unless we have a close relationship with the animal in question. That is, when talking about pets, it is okay to refer to them as "she" or "he". The same applies to "who" and "whom". Yet, in this case, in the first part of the sentence the horse is referred to as "its", so in the second part of the sentence we should also stick to that choice and use the same pronoun.
