Which statement is true of the Berlin Conference?

The Berlin Conference of 1884?85 was a meeting between European nations to create rules on how to peacefully divide Africa among them for colonization. The conference was convened by Portugal but led by Otto von Bismarck, chancellor of the newly united Germany. 

The 14 countries that attended included all the major European powers, as well as Russia, Turkey and the United States. The conference began with a dispute about the Congo River basin.Slavery was forbidden throughout Africa. The attendees agreed upon a principle of effective occupation by which rights over African colonies would be assessed.

Before the conference, about 80 percent of African territory was still in local hands. By 1902, European powers controlled 90 percent of Africa.