Concept:Sparse population in the Middle Belt is caused by physical and economic disadvantages, not by southern slave trade activities.
Explanation:Sparse population means fewer people live in the area.
The Middle Belt has poor soil, which limits crop farming.
It lacks major minerals, so mining is not developed there.
There are also no major industries to attract employment.
European slave trade occurred mainly in the southern coastal regions.
Hence, slave trade cannot explain the low population of the Middle Belt.
Answer:D. Slave trade