These countries were considered to be the only independent areas free from european control during the 1800's
a). nigeria and rwanda
b). ethiopia and nigeria
c). ethiopia and liberia
d). nigeria and mozambique

C). Ethiopia and Liberia

Explanation:

Most of the European countries that were likely to colonize the Africa were those of the rivalry between the African readers and European power took easy control of the lands due to the force and the violence and thus by the 1900 a large part of the Africa land was colonized by mainly seven European powers such as the Britain, then France, then Germany, then Belgium, Spain, Portugal, and the Italy.

I'm pretty sure it's c. extremely gradual but not 100% sure though.