The correct answer is D. Fourteen European nations and the United States divided the African continent for colonization.
This conference basically provided an international legal framework for the Scramble for Africa, the complete colonization, division and sometimes annexation of the African continent during the second half of the 19th century. This colonization and occupation was of course due to economic and political interests. European powers required raw materials and cheap labor to produce goods for the metropolitan territories. They also required the expansion of markets for European products and such economic expansion allowed them to increase their military might as well.
There were a few positive aspects of such maneuverings, since they also tried to sway international public opinion to support colonization. One of these was the international prohibition of slavery by African and Islamic powers.
The declining Ottoman Empire participated to oversee its interests in Northern Africa, mainly Egypt.
The United States participated as an observer, reserving the right to reject or accept the final agreements of the conference.