Which government action is most closely associated with the efforts of muckrakers

Assuming that this is referring to the same list of options that was posted before with this question, the correct response would be the "Passage of the Meat Inspection Act," since it was the Muckrakers who helped expose the danger of a lack of inspection in this area. 

Proxy war were the result of when the opposing forces used 3rd parties as a subtitute for fighting to each other.