Answer: (all answers below are word for word)
Part A: The cartoon shows three white men holding down a black man with their feet. The black man is most likely a formerly enslaved person. The US flag is trampled on the ground. One of the white men is a soldier. One is a worker with a beer bottle in his pocket. The third one is dressed as if he may be wealthy.
Part B: The cartoon's title is about the government that white men created in the south. And the white men in the scene are brutally keeping the black man down. So, I think Nast is saying that the white men in the south will fight hard to make sure their government keeps black people down.
Part C: Southerners passed the black codes to keep black people from having rights. All three men in the cartoon represent the white Southerners who supported these codes. It shows how white people wanted to block the rights of the newly freed black people.
Part D: The artist seems to be sympathetic toward the black man in the cartoon. A US flag lies trampled next to him on the ground. This detail suggests that what the white men are doing is un-american. The white men look mean and threatening. And they have weapons, while the black man does not.