You can try starting with a question, fact, or sound affect to help grab a reader's attention, but it should fit well with your topic.
Answer:
The tone and attitude of the poem changes throughout the poem.
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.