The correct answer is B) It passed the Enforcement Acts.
What the government did to reduce violence against African Americans after the Civil War was that it passed the Enforcement Acts.
The abolition of slavery was already in place but in the Southern States, the reality was different. The government had to do something to protect black people in the South and it decided to pass the Enforcement Acts, three bills from 1870 to 1871. The acts allowed black people to vote in elections, to hold office, receive the protection of the law and serve on juries.
The other options of the question were A)It started Reconstruction. B) It ratified the Fifteenth Amendment.
