The correct answer is the A) Gilded Age.
The era of American history in which these terms and people are MOST closely associated is the Gilded Age.
American writer Mark Twain used the term Gilded Age in his novel "The Gilded Age: A Tale of Today," written in 1873. During this era, the creation of monopolies made some people very rich in America, as was the case of John D. Rockefeller with his Standard Oil Company that bought almost all of his competitors to have the monopoly of oil in the United States. The same case with Andrew Carnegie, with his Steel Company.