PLS HELP TIMES TEST Which advancement in science most contributed to the successful colonization of Africa by European powers in the late 19th century?

a vaccine for yellow feverand understanding of the relationship between religion and well beingan understanding of the relationship between germs and diseasethe cure for polio

monopolies  came to the united states with the colonial administration. the large-scale public works needed to make the new world hospitable to old world immigrants required large companies to carry them out. these companies were granted exclusive contracts for these works by the colonial administrators. even after the american revolution, many of these colonial holdovers still functioned due to the contracts and land

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using the media to encourage public support for an idea.

encouraging congress to take action

establishing a public policy goal for the nation