Answer: C. the proposal that the Nebraska Territory would decide for itself whether to allow slavery.
Step-by-step explanation:
The concept of popular sovereignty states that only the residents of the territory can choose whether or not slavery is allowed.
The Kansas-Nebraska Act (1854), proposed by Stephen A. Douglas, stated popular sovereignty to recognize the settlers´ right to make that decision within the new state. This act raised rather than reduced sectional conflicts, leading to Bleeding Kansas, a period of violence foregoing the American Civil War.