What key role did the region around the Niger River play in trans-Saharan trade?
A
The region produced gold, which was traded for salt produced in North Africa that was then transported to sub-Saharan Africa.

B
The region produced salt, which was traded for gold produced in North Africa that was then transported to sub-Saharan Africa.

C
The region produced glass, which was traded for slaves from North Africa who were then transported to sub-Saharan Africa.

D
The region produced gold, which was traded for goods made in North Africa that were then transported to sub-Saharan Africa.