To accurately answer your question, I would need to see the specific timeline you are referring to. However, I can provide general information for each option you've provided.
If the timeline focuses on events such as the establishment of segregation laws post-Civil War, then it would illustrate A. the implementation of Jim Crow laws in the South.
If it shows events leading up to the Civil War that involved economic disputes, it would illustrate B. increasing tensions over tariffs prior to the Civil War.
If it represents the period immediately following the Civil War where efforts were made to integrate formerly enslaved people into society, it would indicate C. the implementation of Reconstruction in the South.
Finally, if the timeline includes significant events like the Missouri Compromise, the Kansas-Nebraska Act, or other actions related to the expansion of slavery, then it would correspond to D. increasing tensions over slavery prior to the Civil War.
Please provide more context or details from the timeline so I can assist you more accurately.