The correct answer is C.
The central idea of this passage is that the US needs to grant its black population freedom and equality.
Douglass makes the argument that this country cannot reach its maximum potential if a good portion of the population is oppressed. He compares the oppression of African-Americans in the United States to cutting off the right arm of every soldier going to war -- senseless and dangerous.
You need to attach an image of the passage so I can read it.
