which event caused a decrease in trans-saharan trade

Athe settlement of Timbuktu
Bthe ban on slavery in Africa
Cthe collapse of the Umayyad Caliphate
Dthe increase in coastal trade with Portugal

Verified Answer :

The correct answer is letter D. the increase in coastal trade with Portugal. It caused a decrease in Trans-Saharan Trade. Trans-Saharan trade needs to travel across the Sahara until you will reach the sub-Saharan part of Africa. Its peak of trade runs from the 8th century towards the early 17th century. The Portuguese journeyed towards the coastal areas of West Africa, opening new avenue in trade..

D..the increase in coastal trade with portugal