Slavery increased in Southern states as Northern states took steps to end it. Which answer best explains how this division affected Westward expansion?

A) Existing states fought to keep their slaves from moving westward
B) Existing Southern states were finally convinced to abolish slavery,
C) Existing states fought over whether to not slavery should be allowed in the new territories.
D) Existing states did not want their slaves to join forces with Native Americans from the West.