Based on the information given, the lines that illustrate the idea is "Remember, Christians, black as Cain, may be refined and join the angelic train".
A central idea simply means the main idea that's conveyed in a story. It's what the author wants the readers to know.
In this case, the lines from "On Being Brought from Africa to America that convey the idea that all people are deserving of salvation is Remember, Christians, black as Cain, may be refined and join the angelic train".
Learn more about central ideas on:
https://brainly.com/question/2684713
