The correct answer is:
Carnegie Steel.
Andrew Carnegie used vertical integration, meaning he bought all the industries he needed to run his business, so he wouldn't have to continuously purchase goods he needed.
Explanation:
Completely its operation, Carnegie steel continually bought out all the encouraging small business in the steel industry to limit them from becoming their competitor. This way, they became the sole producer in steel industry during that period it was a steel producing association primarily made by Andrew Carnegie and a few close partners, to oversee organizations at steel processes in the Pittsburgh, Pennsylvania range in the late nineteenth century.
