it does not say the horses eat an apple. it says the horses eat the apple. they want us to translate what they say, not what we would like. This way we learn the vocabulary and verb tenses.
can anyone briefly explain the difference between the pronunciation of Spanish in Spain versus Mexico?
I'm sure it is an issue that is not easy to post here because there are differences in all the Spanish speaking countries. I will start you off with a couple of references, and then you can search the internet for more if these do not satisfy your question.