Many Postcolonial Countries, Especially in Africa, Formed When

Many postcolonial countries, especially in Africa, formed when

A) indigenous tribes united to overthrow colonial powers and found their own countries.
B) colonial powers lumped and separated indigenous groups into arbitrary countries.
C) war between eastern and western Africa eventually divided the continent into countries.
D) Colonial powers tried to form countries based on keeping indigenous people of the same culture together in the same country.
E) None of the above is correct.