Moving from coastal to interior regions of sub-Saharan Africa, we discover that the dominant physical-geographic feature is 

A. many coastal inlets.
B. mountainous terrain.
C. ascending plateaus.
D. lush rainforest.

C?

The dominant physical-geographic feature is A. ascending plateaus.

Yes, C.

To determine the dominant physical-geographic feature of moving from coastal to interior regions of sub-Saharan Africa, we can use our knowledge of the geography of the region.

Sub-Saharan Africa is known for its diverse landscape, but in general, as we move from the coastal areas towards the interior, one of the dominant physical-geographic features that becomes more apparent is the presence of ascending plateaus.

These ascending plateaus are often referred to as the African Plateau. This vast highland region covers much of the interior parts of sub-Saharan Africa. The plateau consists of a series of step-like plateaus at varying elevations, with escarpments and flat-topped mountains known as inselbergs.

The ascending plateaus in sub-Saharan Africa create a gradual increase in elevation as we move away from the coast, resulting in a change in climate, vegetation, and also affecting the patterns of rivers and drainage systems.

Therefore, the correct answer is C. Ascending plateaus.