The correct answer is "Silk and Salt were the two main items traded in Ghana".
The Wagadou Empire or Empire of Ghana was a Western African civilization which lasted from 700 to 1240 AD. It was located in what is now the countries of Mauritania and western Mali. There was a growing trade network of salt and gold which the Wagadou knew how to exploit well. The empire rose to prominence by establishing trade routes for these goods, which ended up being very profitable.