Final answer:
Rockefeller, Carnegie, and Morgan are considered robber barons due to their unethical business practices like monopolies, despite their philanthropic endeavors.
Step-by-step explanation:
John Rockefeller, Andrew Carnegie, and J.P. Morgan would be considered robber barons because they engaged in unethical business practices and monopolies, which is captured in option C. These industrialists utilized methods such as horizontal integration, aggressive business tactics, and establishing monopolies which led to significant criticism, especially concerning the impact on the working class and competition. While these tycoons also made substantial philanthropic contributions, the term robber baron highlights their corporate wrongdoing and the extreme tactics they used to create their wealth and consolidate their power.