Final answer:
Colonial powers' interests were most often used to draw new boundaries for African countries.
Step-by-step explanation:
The most common method used to draw new boundaries for African countries was A) Colonial powers' interests. During the colonization of Africa, European powers divided the continent according to their own desires and interests, without consideration for established Indigenous territories and spheres of political influence. The national boundaries were created with the aim of exploiting Africa's resources, rather than considering the people who lived there.
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