Pleaaase will up vote 30 points

the map below shows kingdoms, cities, and trade routes of africa in the period 700–1600 ce. use the map to answer the following question:

which of the following statements is supported by the map?

a: there was a lower volume of trade in northern and western africa, compared to the rest of the continent.

b: at songhai, gold was the major export, while at mogadishu slaves and ivory were.

c: trade routes were concentrated in the northern and western kingdoms, but trading occurred throughout the continent.

d: trade from mobasawa was conducted by land, while trade in kongo was conducted solely by boat.