The act of allowing a state to decide an issue, such as slavery, through voting is known as B) Popular Sovereignty.
Step-by-step explanation:
This concept was popularized during the mid-19th century in the United States as a way to determine whether new territories would be free or slave states. It allowed the people living in those territories to vote on the issue, rather than having it determined by the federal government. The idea of popular sovereignty was a controversial one, as it effectively allowed the continuation of slavery in some areas, which many abolitionists believed was morally wrong. Nevertheless, it was a key component of several important pieces of legislation, including the Kansas-Nebraska Act and the Compromise of 1850.