Answer:
D. All of the above
Step-by-step explanation:
The opening of Africa to Western exploration and exploitation had begun seriously at the end of the sixteenth century. By 1835, Europeans had mapped most of northwest Africa. Among the most famous European explorers were David Livingstone, who drew plans for the vast interior, and Alexandre de Serpa Pinto, who crossed it into a complicated expedition, mapping the interior of the continent. Arduous expeditions in the 1850s and 1860s by Richard Burton, John Speke and James Grant discovered the great central lakes and the birth of the Nile River. By the end of the century, the Europeans had mapped the Nile since its birth, the River Trail Niger, the Congo and Zambezi rivers had been traced, and the world had discovered the great resources of Africa.
In any case, at the beginning of the struggle for the possession of Africa, Western nations controlled only 10 percent of the continent. In 1875 the most important controlled territories, both in terms of size and wealth, were Algeria, under the control of France; the Cape Colony, controlled by the United Kingdom; and Angola, which was dominated by Portugal.
Technological advances facilitated expansion over long distances. Industrialization caused rapid advances in transport and communications, especially in steam navigation, railways and telegraphs. Medical advances were also important, especially medicines for tropical diseases. The development of quinine, an effective treatment against malaria, allowed the vast region of the tropics to be accessible to Europeans.