The best answer that shows how the issue of states' rights contributed to the onset of the Civil War is:
Many southerners believed the rights of their states were threatened by Northern abolitionists.
This option highlights the South's perspective that their states' rights were under threat from Northern efforts to abolish slavery, which they viewed as a direct challenge to their autonomy and way of life. This conflict over states' rights and the federal government's role in issues such as slavery was a significant factor leading to the Civil War.