How was Social Darwinism connected to the turn-of-the-century imperialism of the United States?

a. Social Darwinism confirmed the idea that Americans were more capable than European nations in educating and civilizing primitive cultures.
b. Imperialists believed it was the duty of the white citizens of the United States to civilize indigenous cultures, in order to become a democratic society.
c. Social Darwinism led supporters of imperialism to believe that "lesser" nations were not as fit as the United States to compete in world trade.
d. Imperialists believed the United States could not educate or civilize the people of "lesser nations" because of language and cultural barriers.