The answer is:
A. They had a strong military and became the largest empire in West Africa.
Shonghai was a wealthy and powerful empire, which expanded from Mali westward to the Atlantic Ocean and northward. Therein, Ali Ber was the first king of the Songhai Empire who came to power in 1464. Besides, he kept mounted warriors to protect the land and had a fleet of war canoes patrolling the Niger River.