The option that best explains the religious demographics in northern and southern Africa is:
A. conquest of the north by Arab Muslims and colonization of the south by European Christians.
This choice reflects the historical context where Arab Muslim conquests significantly impacted the religious landscape in North Africa, establishing Islam as the predominant faith in that region. Conversely, the colonization efforts by European powers in sub-Saharan Africa often included missionary work that spread Christianity, making it more prevalent in the southern parts of the continent.