Sub-saharan africa is studied as a region because
a.
most people speak the same language
b.
most people belong to the same ethnic group
c.
it is isolated from north africa by the sahara desert
d.
most people practice the same religion

C.it is isolated from North Africa by the Sahara Desert

Explanation:

Region can be divided by different ways, by the language they speak, by the religion they practice, by the country or type of government that they beling to, or because of their geographical barriers, in this case the Sahara Desert isolates the sub sharan region and it has certain characteristics because of that and that allows the scientists to study that region separetly.