The correct comparative to the adverb healthfully is more healthfully, and the superlative is most healthfully. As has been pointed out admirably elsewhere in this post, healthfully is not a commonly used adverb. However, that does not make it incorrect to use it.
The question is a bit vague, but I'd say D because a monster who saves a child and then gets shot by the father would surely contribute to "monsters' hatred of humans"
