As african merchants traded with people in the middle east prior to the 1500s,
a) many african states began to feel threatened by outside cultures and withdrew to isolation.
b) islam spread to west africa, combining with african religions to form the dominant faith.
c) merchants brought back plagues that destroyed much of west african population.
d) african states refused to meet world demands for slave populations.

B) Islam spread to West Africa, combining with African religions to form the dominant faith. Africa was the first area for Islam to spread from where it started in western Asia. North Africa saw a great deal of Islamic influence be spread by means of trading along the Trans-Sahara trade that saw gold, salt, ivory, etc between those in North and West Africa with those in the Middle East who made contact by exploration. This Islamic influence helped set a base for certain African communities to be based on Muslim principles.