Answer: A) that people of African descent are no less human than white settlers and should be treated respectfully.
Explanation: In the given excerpt from "The Selling of Joseph" we can see the description of Ethiopians as Sons and Daughters of the First Adam, this means that it doesn't matter what color of the skin they have, all humans must be equal in rights, so the Sewall's assertion in this excerpt is that people of African descent are no less human than white settlers and should be treated respectfully.
Climax this may be wrong but 99.999 % sure its right