It would be Because of the Air Force
The answer to your question is A
I believe it is b, I'm not sure though.
Explanation:
The Mason-Dixon line was essentially one of the most used underground 'lines' of railroad to transport slaves to freedom. It was a railroad that, although not important before, became incredibly important over time as it was an essential 'Forgotten' railroad in a way, that was not only able to transport slaves, but had tracks directly into and through both free and slave states.
[I hope this helps:)]
