Accurate maps and sea charts helped them
Letters would be an example of a primary source
To advise the President on domestic and international affairs.
Answer:
The trans-Saharan trade was an important gateway for the spread of Islam in Africa. The legacy of the medieval empires and nineteenth century reform movements continues to have relevance in present day Senegal, Gambia, Mali, Nigeria, Burkina Faso, Nigeria, as well as many neighboring communities. The main items traded were gold and salt. The gold mines of West Africa provided great wealth to West African Empires such as Ghana and Mali. Other items that were commonly traded included ivory, kola nuts, cloth, slaves, metal goods, and beads.
Over the last 20-25 years there has been many terist attacks around the around the world like 9/11 the bombing of Pearl Harbor and many more but now we have not seen or heard of any terist but they did catch some so in my opinion it reduced.