What was a major cause of regional conflicts in the United States when Kansas and Nebraska were added as new territories?
O A. Northerners worried that the new territories would support Republicans.
O B. Southerners claimed that the new territories were too large.
C. Southerners believed that neither territory should become a state,
D. Northerners wanted both tewtories to outlaw slavery

I would say A due to what I wrote below but im not to sure so please check but im sure its A

The conflicts that arose between pro-slavery and anti-slavery settlers in the aftermath of the act's passage led to the period of violence known as Bleeding Kansas, and helped paved the way for the American Civil War (1861-65).

Explanation:

the exclusive possession or control of the supply or trade in a commodity or service.