Final answer:
Frederick Douglass believed that African Americans must fight to prove themselves worthy of citizenship.
Step-by-step explanation:
From the excerpt, we can infer that Frederick Douglass believes that African Americans B. must fight to prove themselves worthy of citizenship. In the quote, Douglass states, ‘Once let the black man get upon his person the brass letters U.S. . . . and a musket on his shoulder and bullets in his pocket, and there is no power on earth that can deny that he has earned the right to citizenship.’ This implies that African Americans need to demonstrate their commitment to the country by serving in the Union armed forces to rightfully earn their citizenship.