Ghana, Mali, and Songhai were A. large oases in the Sahara.
B. poor countries in coastal West Africa.
C. important leaders in Central Africa.
D. ancient empires in the Sahel.

c

Explanation:

the precambrian aged rocks could be found in australia. australia is a region that has a lot of ancient civilization history from million years ago. in this region, there are a lot of recognizable fossils buried in its land which is considered a precambrian-aged rocks

answer ( groundwater);