Answer:
B. It stands for the pain of slavery that nearly a century of struggle for civil rights has not erased.
Step-by-step explanation:
Hello! The poem is about racism, referring to the slavery that African Americans suffered throughout history. The author describes himself as locked in a cage that oppresses him. The quoted extract alludes to the scars left by those dark times of violence against people, which still persist in other ways, for example, racial hatred.