Answer: C. It allowed the election of former Confederate soldiers to public office.
Step-by-step explanation:
Andrew Johnson is often seen as one of the worst presidents in US history and this mostly stems from his opposition to the civil liberties that were to be granted to former enslaved blacks after the conclusion of the Civil War.
After the war, Johnson presented a plan for reconstruction that favored the Southern States because it allowed them control over their own civilian governments which enabled them to deprive black people of their rights once more. Another direct effect of this however, was that it allowed the South to elect former confederate soldiers to public office which infuriated the Republicans in Congress.