Which of the following geographical regions of Nigeria covers one-fifth of the country and has a generally flat surface dotted with granitic hills? The

The geographical region of Nigeria described in the question is the North-Central Highlands. This area covers about one-fifth of the country and is characterized by a generally flat surface with granitic hills, known as inselbergs, scattered throughout the landscape. These hills are composed of hard rock formations that have resisted erosion, thereby standing out from the flatter surroundings.

This region is situated in the north-central part of Nigeria and is significant for its geological features and agricultural potential. The flat terrain provides an expansive area suitable for farming, while the inselbergs add to the region's natural beauty and sometimes serve as landmarks. The North-Central Highlands are an important and distinct geographical region within Nigeria due to these unique characteristics.