Answer:
Option C, by proposing these territories be allowed popular sovereignty, is the right answer.
Explanation:
An act through which the territories of Kansas and Nebraska were created was known as the Kansas–Nebraska Act of 1854. Drafted by Stephen A. Douglas, a Democratic Senator, this act was passed by the 33rd Congress of the United States and signed by  Franklin Pierce, the then U.S. President.
Since many of the Southern leaders refused to allow the formation of slavery banned territory, Douglas agreed to repeal the Missouri Compromise in order to win the support of the Southerners and by proposing these territories be allowed popular sovereignty.
