How Were Many Postcolonial Countries, Especially in Africa, Formed

How were many postcolonial countries, especially in Africa, formed?

A) Indigenous tribes united to overthrow colonial powers and found their own countries.
B) Colonial powers lumped and separated indigenous groups of people into arbitrary countries.
C) War between eastern and western Africa eventually divided the continent into countries.
D) Nation-states were formed in Africa long before colonialism and remained distinct.
E) Colonial powers tried to form countries based on keeping indigenous people of the same culture together in the same country.