The correct option is A Mali
In the ancient empire of Mali, the most important industry for trading was the gold industry. Much gold was traded through the Sahara desert, to the countries on the North African coast. The traders would travel by caravans, on camels. All of the things that Mali traded gold for helped them stay very wealthy. In extending Mali’s rule beyond Kangaba’s narrow confines, Sundiata set a precedent for successive emperors. Imperial armies secured the gold-bearing lands of Bondu and Bambuk to the south, subdued the Diara in the northwest, and pushed along the Niger as far north as Lac Débo. Under Mansa Mūsā (1307–32?) Mali rose to the apogee of its power. He controlled the lands of the Middle Niger, absorbed into his empire the trading cities of Timbuktu and Gao, and imposed his rule on such south Saharan cities as Walata and the Taghaza region of salt deposits to the north. Hence, Option A is correct. Among the rest, the Mongol empire was based in Mongolia in Central Asia. Ottoman Empire was based in Turkey. Abbasid Empire was based in the Indian subcontinent. Hence, these are incorrect.