Who were some of the business and industrial titans of the late nineteenth century, and what did they contribute to america's industrial growth?

We can name the John D.  Rockefeller and the Oil company, Andrew  Carnegie and the Steel company, and J. P. Morgan in the financial field. the government encouraged national growth by imposing a high tariff on imported products and granting railroad companies public land. Those features created the leading entrepreneurs, who were extraordinarily skilled at organizing and controlling industry. John D. Rockefeller controlled almost every phase of the oil industry, via trusts and holding companies.  Andrew Carnegie dominated the steel industry by buying striving companies, and J. Pierpont Morgan, an investment banker, controlled most of the nation’s railroads.

answer; ///i do believe that the correct answer is (b) ///middle colony