Answer: D. People in the North organize to stop the spread of slavery
Step-by-step explanation:
The Northern states had acted to abolish slavery in their own states and were against the practice unlike in the South where slavery was considered a way of life. These two wanted to spread their doctrines to the western territories so as to gain more influence.
This is why people in the North organized to stop the spread of slavery when the South wanted to spread it to the west leading to a very politically divided nation that would eventually go to war.