The correct option is C Pygmies
The basin was the watershed of the Congo River populated by pygmy peoples, and eventually Bantu peoples migrated there and founded the Kingdom of Kongo. Belgium, France, and Portugal later established colonial control over the entire region by the late 19th century. The General Act of the Berlin Conference of 1885 gave a precise definition to the "conventional basin" of the Congo, which included the entire actual basin plus some other areas. The General Act bound its signatories to neutrality within the conventional basin, but this was not respected during the First World War.