What makes a source credible

The correct answer is letter D

Ghana was one of the largest empires formed on the African continent that developed outside the coastal regions or Muslim Africa. Its area corresponded to the current regions of Mali and Mauritania, bordering the immense Sahara desert. From now on, we understand the instigating history of a kingdom that prospered even though it does not have outlets to the sea and is close to a region considered economically unfeasible.

The Mali Empire was an African state located in North West Africa, close to the River Niger, and which had its dominion during the 13th and 14th centuries. It was an empire out of three in a row that dominated the region, and among them, the Mali Empire was the most extensive territorially compared to the other two, Songhai and Ghana.

Following a chronology we can list the Songhai Empire as the first empire that gained dominance under the Niger River region, followed by the Empire of Ghana that disappeared around 1076 when a Berber and Muslim government was imposed until in 1240, the Mali's king, Sundiata Keita, went and conquered them. Immediately after this decay and conquest, the Empire of Mali rose, which is considered the largest, the largest of all medieval African empires.