Which one of the following is a part of the Congo Basin?

Cameroon is correct because it is one of the six countries—alongside the DRC, ROC, CAR, Gabon, and Equatorial Guinea—that share the Congo Basin's drainage area. Uganda is a common distractor due to its proximity to the DRC, but it is geographically situated almost entirely within the Nile Basin. This question tests the core concept of major global river basins and regional African geography.