Answer: I believe it is A. Not entirely sure though... Have a nice day anyway!
Explanation:
The voice that you hear in a story is the voice of the narrator, and told either in first person or third-person. Details tell you how the narrator feels about the characters and events. From the first page of "How Mighty Kate Stopped the Train," I see that the story is told from the third-person point of view.
The main reason the United States government intervened in the Great Railroad Strike of 1877 was because it was leaving thousands of people without transportation, which meant that the US GDP was decreasing in hurting business of all kinds.