Answer :
The source for study of the slave trade would be most unusual if it were a primary source description written by a slave. Hence, Option C is correct.
What is the slave trade?
Slavery has existed since ancient times and is something that exists in the present world also. Capturing, selling, and buying people in legal and illegal terms are covered by the slave trade.
According to a group named "American Anti-Slavery Group", claims that more than 40 million people are the victims of this slave trade around the world.
Therefore, Option C: A primary source description written by a slave is the most unusual source for slave trade studies.
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