The correct answer is “mining” (C). As you may know, mining is the act, process, or industry of extracting ores, coal, etc., from mines. The West was brushed by a huge change after the Civil War. As railroads increased access, settlers, ranchers, and miners always transformed millions of acres of western land. Mining was the first great boom in the West. Gold and silver were the key that attracted a massive number of people. Prospectors from the East were just a part of a deluge that included people from all around the world.