Concept:Assimilation policy was the main obstacle because it divided the educated African elite and weakened nationalist unity.Explanation:France used the assimilation policy to turn a small number of educated Africans into French citizens.These Africans were given French rights, status, and privileges, making them loyal to France instead of their own people.This “bought off” the potential leaders of nationalist movements, so they did not push for independence.As a result, the nationalist struggle in French West African colonies was greatly slowed down because its natural leaders were no longer opposed to French rule.Answer:B. assimilation policy