Final answer:
By 1914, European countries controlled about 90% of Africa, primarily because of the Scramble for Africa and the decisions made at the 1884 Berlin Conference.
Step-by-step explanation:
By 1914, Europeans had established control over approximately 90 percent of the African continent, a significant increase from about 10 percent at the beginning of the Second Industrial Revolution. During the "Scramble for Africa", a period of aggressive competition among European nations, territories were claimed and boundaries drawn that largely ignored the established social and cultural divisions between African societies.
The 1884 Berlin Conference was a key event in this process, where European powers met to divide Africa without the involvement of African representatives. This led to the exploitation of Africa's rich natural resources, with the indigenous populations seeing few benefits, as their resources were extracted and profits flowed back to Europe.