Answer :
"The South had more immigrants in large cities" was not a reason for the growing division between North and South after 1820, since the North had far more immigrants.
The correct answer is C) The South had more immigrants in large cities.
During the middle of the 19th century, it was the Northern cities that were becoming more industrialized. This increased industrialization resulted in the need for a large workforce. This is why many immigrants ended up in large cities in the North. A perfect example of this would be New York city.
All of the other options do represent issues between the North and South at this time, as their differing economies and views on slavery would continue to lead to problems. This eventually lead to the beginning of the Civil War.