Answer:
Salt and Gold
Explanation:
This was often referred to as the GOLD-SALT trade. The West African kingdoms have an abundance of golds.
This is evident in Ghana till the present moment and Mali during the time of Mansa Musa in the 14th century.
On the other hand, the Arab merchants have abundant salt for trading due to their nearness to the sea.
Hence, the right answer, in this case, is the trade was primarily based on SALT and GOLD.
