What Was the Nature of Trade with the Towns of East

What was the nature of trade with the towns of east Africa?

A) Most trade was focused on caravans crossing the Sahel to north Africa.
B) Trade was limited to local commerce among the towns and with the hinterlands lying west of the urbanized coast.
C) There was active trade to the Persian Gulf and Egypt, but little beyond those points.
D) International trade flourished in the urbanized ports of east Africa, including commerce with India and China.