"I like love stories."
Translation:Me gustan las historias de amor.
Spanish, differently from English, uses definite articles when you speak about ALL the objects in the specified group. Since the sentence implies that you like all love stories, you have to use the definite article here. This usage may seem quite counter-intuitive for an English speaker, but you will have to get used to it.
"I like" does not translate well to "me gustan". When you say "I like" in spanish you can't think of it as "I enjoy", you need to think of it as "they are pleasing to me."
"I" translates to "Yo", but they're not using "Yo", they're using "me". You can think that "I enjoy" translates to "Yo disfruta", in which case you might safely say "Yo disfruta historias de amor." without the las (someone can correct me on this, not sure on it)
But when you're using the "me" in "me gustan", you're saying "(they) are appeasing to me"
I figure that's why they give us the three hearts. For every ten questions, I miss one or two with answers that would not be incorrect in speech but they didn't think of it when entering the correct alternatives. In this case you should of known they would use "el amor" as in other items.
In this case, the stories are the ones doing an action; "gustar" is more literally "to please", so this sentence would be more like "the love stories are pleasing to me" if you translated it literally.
("Gustan" is used for plural subjects, as the stories are here.)
Since we never say things like that in English, they translate it to the way we normally would say it.