What did secede or secession mean with regard to the Southern states of the Union?
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Secession was the act by which a state left the Union. The Secession Crisis of late 1860 and early 1861 led to the Civil War when southern states seceded from the Union and declared themselves a separate nation, the Confederate States of America. There is no provision for secession in the U.S. Constitution.

Explanation:

letter a is the answer

a. favoring native born americans over immigrants.