B .The Vietnamese adopted the civil service exam.
Answer:
Explanation: It is true that allegiance to a tribe is one handicap to national unity in Africa. When Africa was divided into countries, it did so with little consultation of local people.
Plantation owners turned to the enslaved Africans as a labor force because they were not paying them for their work, instead they were just providing shelter and food for them. Also, they had total control over them because they owned them, thus were able to make them work as much as they wanted and the slaves couldn't do anything about it.
D. All of the above
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