Many historians agree that westward expansion was indeed the primary source of contention between the North and South in the sense that it made the question os slavery unavoidable. Each new state had to be determined slave or free--leading to disagreements that led to the Civil War.
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Explanation:
it makes the most sense to me, but choose whatever you think is right.
The abbreviation for before the birth of Christ is B.C.
It stands for "before Christ".
Hope this helps :)
