The Laikipia district in Kenya is one of the most unique ecosystems

Something is either unique -- unlike everything else -- or it's not. A thing can't be "more unique" than another, or the "most unique" thing in the world. So the beginning of every answer choice is problematic, and the sentence becomes more problematic still once we learn the district is "one of the few places" where farmers and predators coexist, which means it is not "unique" at all. The answer should be E, since it's "the places" that provide the "stable coexistence", so we need a plural verb conjugation, and we probably want to preserve the phrase "in the world", though C isn't really all that bad either if you ignore the misuse of language throughout.