Read the excerpt from "What to the Slave is the Fourth of July?” Are the great principles of political freedom and of natural justice, embodied in that Declaration of Independence, extended to us?

How does this rhetorical question contribute to the passage’s central idea?
It encourages African Americans to discuss the principles set forth in the Declaration of Independence.
It reinforces the idea that the rights given to others are not extended to African Americans.
It reveals that Douglass has an in-depth knowledge of the Declaration of Independence.
It gives the rest of the speech importance by referring to a famous historical document.